diff --git a/eras/alonzo/impl/CHANGELOG.md b/eras/alonzo/impl/CHANGELOG.md
index 09cf2099d4a..750666fcfd3 100644
--- a/eras/alonzo/impl/CHANGELOG.md
+++ b/eras/alonzo/impl/CHANGELOG.md
@@ -12,6 +12,10 @@
 * Remove `witsVKeyNeeded`, in favor of the one from `cardano-ledger-shelley`
 * Fix an issue where `TotalDeposits` didn't appear on Alonzo era
 
+## 1.2.1.0
+
+* Fix `PParams AlonzoEra` serialization. [#3440](https://github.com/input-output-hk/cardano-ledger/pull/3440)
+
 ## 1.2.0.0
 
 * Replace `DPState c` with `CertState era`
diff --git a/eras/alonzo/impl/src/Cardano/Ledger/Alonzo/PParams.hs b/eras/alonzo/impl/src/Cardano/Ledger/Alonzo/PParams.hs
index cb7301fcd34..2dee59a37cf 100644
--- a/eras/alonzo/impl/src/Cardano/Ledger/Alonzo/PParams.hs
+++ b/eras/alonzo/impl/src/Cardano/Ledger/Alonzo/PParams.hs
@@ -84,11 +84,16 @@ import Cardano.Ledger.Binary (
   Encoding,
   FromCBOR (..),
   ToCBOR (..),
+  decCBORGroup,
+  decodeRecordNamed,
+  encCBORGroup,
   encodeFoldableAsDefLenList,
   encodeFoldableAsIndefLenList,
+  encodeListLen,
   encodeMapLen,
   encodeNull,
   encodePreEncoded,
+  listLen,
   serialize',
  )
 import Cardano.Ledger.Binary.Coders (
@@ -101,7 +106,6 @@ import Cardano.Ledger.Binary.Coders (
   encode,
   field,
   (!>),
-  (<!),
  )
 import Cardano.Ledger.Coin (Coin (..))
 import Cardano.Ledger.Crypto (Crypto)
@@ -278,90 +282,63 @@ instance Crypto c => EraGovernance (AlonzoEra c) where
   getProposedPPUpdates = Just . proposals
 
 instance Era era => EncCBOR (AlonzoPParams Identity era) where
-  encCBOR
-    AlonzoPParams
-      { appMinFeeA
-      , appMinFeeB
-      , appMaxBBSize
-      , appMaxTxSize
-      , appMaxBHSize
-      , appKeyDeposit
-      , appPoolDeposit
-      , appEMax
-      , appNOpt
-      , appA0
-      , appRho
-      , appTau
-      , appD
-      , appExtraEntropy
-      , appProtocolVersion
-      , appMinPoolCost
-      , appCoinsPerUTxOWord
-      , appCostModels
-      , appPrices
-      , appMaxTxExUnits
-      , appMaxBlockExUnits
-      , appMaxValSize
-      , appCollateralPercentage
-      , appMaxCollateralInputs
-      } =
-      encode $
-        Rec (AlonzoPParams @Identity)
-          !> To appMinFeeA
-          !> To appMinFeeB
-          !> To appMaxBBSize
-          !> To appMaxTxSize
-          !> To appMaxBHSize
-          !> To appKeyDeposit
-          !> To appPoolDeposit
-          !> To appEMax
-          !> To appNOpt
-          !> To appA0
-          !> To appRho
-          !> To appTau
-          !> To appD
-          !> To appExtraEntropy
-          !> To appProtocolVersion
-          !> To appMinPoolCost
-          -- new/updated for alonzo
-          !> To appCoinsPerUTxOWord
-          !> To appCostModels
-          !> To appPrices
-          !> To appMaxTxExUnits
-          !> To appMaxBlockExUnits
-          !> To appMaxValSize
-          !> To appCollateralPercentage
-          !> To appMaxCollateralInputs
+  encCBOR AlonzoPParams {..} =
+    encodeListLen (23 + listLen appProtocolVersion)
+      <> encCBOR appMinFeeA
+      <> encCBOR appMinFeeB
+      <> encCBOR appMaxBBSize
+      <> encCBOR appMaxTxSize
+      <> encCBOR appMaxBHSize
+      <> encCBOR appKeyDeposit
+      <> encCBOR appPoolDeposit
+      <> encCBOR appEMax
+      <> encCBOR appNOpt
+      <> encCBOR appA0
+      <> encCBOR appRho
+      <> encCBOR appTau
+      <> encCBOR appD
+      <> encCBOR appExtraEntropy
+      <> encCBORGroup appProtocolVersion
+      <> encCBOR appMinPoolCost
+      -- new/updated for alonzo
+      <> encCBOR appCoinsPerUTxOWord
+      <> encCBOR appCostModels
+      <> encCBOR appPrices
+      <> encCBOR appMaxTxExUnits
+      <> encCBOR appMaxBlockExUnits
+      <> encCBOR appMaxValSize
+      <> encCBOR appCollateralPercentage
+      <> encCBOR appMaxCollateralInputs
 
 instance Era era => DecCBOR (AlonzoPParams Identity era) where
   decCBOR =
-    decode $
-      RecD AlonzoPParams
-        <! From -- appMinFeeA
-        <! From -- appMinFeeB
-        <! From -- appMaxBBSize
-        <! From -- appMaxTxSize
-        <! From -- appMaxBHSize
-        <! From -- appKeyDeposit
-        <! From -- appPoolDeposit
-        <! From -- appEMax
-        <! From -- appNOpt
-        <! From -- appA0
-        <! From -- appRho
-        <! From -- appTau
-        <! From -- appD
-        <! From -- appExtraEntropy
-        <! From -- appProtocolVersion
-        <! From -- appMinPoolCost
-        -- new/updated for alonzo
-        <! From -- appCoinsPerUTxOWord
-        <! From -- appCostModels
-        <! From -- appPrices
-        <! From -- appMaxTxExUnits
-        <! From -- appMaxBlockExUnits
-        <! From -- appMaxValSize
-        <! From -- appCollateralPercentage
-        <! From -- appMaxCollateralInputs
+    decodeRecordNamed "PParams" (\pp -> 23 + fromIntegral (listLen (appProtocolVersion pp))) $ do
+      appMinFeeA <- decCBOR
+      appMinFeeB <- decCBOR
+      appMaxBBSize <- decCBOR
+      appMaxTxSize <- decCBOR
+      appMaxBHSize <- decCBOR
+      appKeyDeposit <- decCBOR
+      appPoolDeposit <- decCBOR
+      appEMax <- decCBOR
+      appNOpt <- decCBOR
+      appA0 <- decCBOR
+      appRho <- decCBOR
+      appTau <- decCBOR
+      appD <- decCBOR
+      appExtraEntropy <- decCBOR
+      appProtocolVersion <- decCBORGroup
+      appMinPoolCost <- decCBOR
+      -- new/updated for alonzo
+      appCoinsPerUTxOWord <- decCBOR
+      appCostModels <- decCBOR
+      appPrices <- decCBOR
+      appMaxTxExUnits <- decCBOR
+      appMaxBlockExUnits <- decCBOR
+      appMaxValSize <- decCBOR
+      appCollateralPercentage <- decCBOR
+      appMaxCollateralInputs <- decCBOR
+      pure AlonzoPParams {..}
 
 instance Era era => ToCBOR (AlonzoPParams Identity era) where
   toCBOR = toEraCBOR @era
diff --git a/eras/alonzo/test-suite/golden/translations.cbor b/eras/alonzo/test-suite/golden/translations.cbor
index b00dfa132b7..4c9951d6e09 100644
Binary files a/eras/alonzo/test-suite/golden/translations.cbor and b/eras/alonzo/test-suite/golden/translations.cbor differ
diff --git a/eras/babbage/impl/CHANGELOG.md b/eras/babbage/impl/CHANGELOG.md
index ddfede1ab52..b57a7c76165 100644
--- a/eras/babbage/impl/CHANGELOG.md
+++ b/eras/babbage/impl/CHANGELOG.md
@@ -8,6 +8,10 @@
 * Add `EraPlutusContext 'PlutusV2` instance to `BabbageEra`
 * Fix an issue where `TotalDeposits` didn't appear on Babbage era
 
+## 1.2.1.0
+
+* Fix `PParams BabbageEra` serialization. [#3440](https://github.com/input-output-hk/cardano-ledger/pull/3440)
+
 ## 1.2.0.0
 
 * Replace `DPState c` with `CertState era`
diff --git a/eras/babbage/impl/src/Cardano/Ledger/Babbage/PParams.hs b/eras/babbage/impl/src/Cardano/Ledger/Babbage/PParams.hs
index 53ae8043889..4738aeecba1 100644
--- a/eras/babbage/impl/src/Cardano/Ledger/Babbage/PParams.hs
+++ b/eras/babbage/impl/src/Cardano/Ledger/Babbage/PParams.hs
@@ -60,6 +60,11 @@ import Cardano.Ledger.Binary (
   Encoding,
   FromCBOR (..),
   ToCBOR (..),
+  decCBORGroup,
+  decodeRecordNamed,
+  encCBORGroup,
+  encodeListLen,
+  listLen,
  )
 import Cardano.Ledger.Binary.Coders (
   Decode (..),
@@ -71,7 +76,6 @@ import Cardano.Ledger.Binary.Coders (
   encode,
   field,
   (!>),
-  (<!),
  )
 import Cardano.Ledger.Coin (Coin (..))
 import Cardano.Ledger.Crypto (Crypto)
@@ -233,61 +237,59 @@ instance Crypto c => EraGovernance (BabbageEra c) where
 
 instance Era era => EncCBOR (BabbagePParams Identity era) where
   encCBOR BabbagePParams {..} =
-    encode
-      ( Rec (BabbagePParams @Identity)
-          !> To bppMinFeeA
-          !> To bppMinFeeB
-          !> To bppMaxBBSize
-          !> To bppMaxTxSize
-          !> To bppMaxBHSize
-          !> To bppKeyDeposit
-          !> To bppPoolDeposit
-          !> To bppEMax
-          !> To bppNOpt
-          !> To bppA0
-          !> To bppRho
-          !> To bppTau
-          !> To bppProtocolVersion
-          !> To bppMinPoolCost
-          !> To bppCoinsPerUTxOByte
-          !> To bppCostModels
-          !> To bppPrices
-          !> To bppMaxTxExUnits
-          !> To bppMaxBlockExUnits
-          !> To bppMaxValSize
-          !> To bppCollateralPercentage
-          !> To bppMaxCollateralInputs
-      )
+    encodeListLen (21 + listLen bppProtocolVersion)
+      <> encCBOR bppMinFeeA
+      <> encCBOR bppMinFeeB
+      <> encCBOR bppMaxBBSize
+      <> encCBOR bppMaxTxSize
+      <> encCBOR bppMaxBHSize
+      <> encCBOR bppKeyDeposit
+      <> encCBOR bppPoolDeposit
+      <> encCBOR bppEMax
+      <> encCBOR bppNOpt
+      <> encCBOR bppA0
+      <> encCBOR bppRho
+      <> encCBOR bppTau
+      <> encCBORGroup bppProtocolVersion
+      <> encCBOR bppMinPoolCost
+      <> encCBOR bppCoinsPerUTxOByte
+      <> encCBOR bppCostModels
+      <> encCBOR bppPrices
+      <> encCBOR bppMaxTxExUnits
+      <> encCBOR bppMaxBlockExUnits
+      <> encCBOR bppMaxValSize
+      <> encCBOR bppCollateralPercentage
+      <> encCBOR bppMaxCollateralInputs
 
 instance Era era => ToCBOR (BabbagePParams Identity era) where
   toCBOR = toEraCBOR @era
 
 instance Era era => DecCBOR (BabbagePParams Identity era) where
   decCBOR =
-    decode $
-      RecD BabbagePParams
-        <! From -- bppMinFeeA
-        <! From -- bppMinFeeB
-        <! From -- bppMaxBBSize
-        <! From -- bppMaxTxSize
-        <! From -- bppMaxBHSize
-        <! From -- bppKeyDeposit
-        <! From -- bppPoolDeposit
-        <! From -- bppEMax
-        <! From -- bppNOpt
-        <! From -- bppA0
-        <! From -- bppRho
-        <! From -- bppTau
-        <! From -- bppProtocolVersion
-        <! From -- bppMinPoolCost
-        <! From -- bppCoinsPerUTxOByte
-        <! From -- bppCostModels
-        <! From -- bppPrices
-        <! From -- bppMaxTxExUnits
-        <! From -- bppMaxBlockExUnits
-        <! From -- maxValSize
-        <! From -- collateralPercentage
-        <! From -- maxCollateralInputs
+    decodeRecordNamed "PParams" (\pp -> 21 + fromIntegral (listLen (bppProtocolVersion pp))) $ do
+      bppMinFeeA <- decCBOR
+      bppMinFeeB <- decCBOR
+      bppMaxBBSize <- decCBOR
+      bppMaxTxSize <- decCBOR
+      bppMaxBHSize <- decCBOR
+      bppKeyDeposit <- decCBOR
+      bppPoolDeposit <- decCBOR
+      bppEMax <- decCBOR
+      bppNOpt <- decCBOR
+      bppA0 <- decCBOR
+      bppRho <- decCBOR
+      bppTau <- decCBOR
+      bppProtocolVersion <- decCBORGroup
+      bppMinPoolCost <- decCBOR
+      bppCoinsPerUTxOByte <- decCBOR
+      bppCostModels <- decCBOR
+      bppPrices <- decCBOR
+      bppMaxTxExUnits <- decCBOR
+      bppMaxBlockExUnits <- decCBOR
+      bppMaxValSize <- decCBOR
+      bppCollateralPercentage <- decCBOR
+      bppMaxCollateralInputs <- decCBOR
+      pure BabbagePParams {..}
 
 instance Era era => FromCBOR (BabbagePParams Identity era) where
   fromCBOR = fromEraCBOR @era
diff --git a/eras/babbage/test-suite/golden/translations.cbor b/eras/babbage/test-suite/golden/translations.cbor
index 4cf4a1014d9..574d1cdeca2 100644
Binary files a/eras/babbage/test-suite/golden/translations.cbor and b/eras/babbage/test-suite/golden/translations.cbor differ
diff --git a/libs/cardano-ledger-binary/src/Cardano/Ledger/Binary/Decoding/Decoder.hs b/libs/cardano-ledger-binary/src/Cardano/Ledger/Binary/Decoding/Decoder.hs
index 1e07810b7c6..4624d8c3cd6 100644
--- a/libs/cardano-ledger-binary/src/Cardano/Ledger/Binary/Decoding/Decoder.hs
+++ b/libs/cardano-ledger-binary/src/Cardano/Ledger/Binary/Decoding/Decoder.hs
@@ -3,7 +3,6 @@
 {-# LANGUAGE DataKinds #-}
 {-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE LambdaCase #-}
-{-# LANGUAGE NumericUnderscores #-}
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE ScopedTypeVariables #-}