diff --git a/domain/miningmanager/mempool/config.go b/domain/miningmanager/mempool/config.go
index 9a34611fa..06cf5a4f7 100644
--- a/domain/miningmanager/mempool/config.go
+++ b/domain/miningmanager/mempool/config.go
@@ -11,6 +11,9 @@ const (
 	defaultTransactionExpireScanIntervalSeconds uint64 = 10
 	defaultOrphanExpireIntervalSeconds          uint64 = 60
 	defaultOrphanExpireScanIntervalSeconds      uint64 = 10
+
+	defaultMaximumOrphanTransactionSize = 100000
+	defaultMaximumOrphanTransactions    = 50
 )
 
 type config struct {
@@ -18,6 +21,7 @@ type config struct {
 	transactionExpireScanIntervalDAAScore uint64
 	orphanExpireIntervalDAAScore          uint64
 	orphanExpireScanIntervalDAAScore      uint64
+	maximumOrphanTransactionSize          int
 }
 
 func defaultConfig(dagParams *dagconfig.Params) *config {
@@ -28,5 +32,6 @@ func defaultConfig(dagParams *dagconfig.Params) *config {
 		transactionExpireScanIntervalDAAScore: defaultTransactionExpireScanIntervalSeconds / targetBlocksPerSecond,
 		orphanExpireIntervalDAAScore:          defaultOrphanExpireIntervalSeconds / targetBlocksPerSecond,
 		orphanExpireScanIntervalDAAScore:      defaultOrphanExpireScanIntervalSeconds / targetBlocksPerSecond,
+		maximumOrphanTransactionSize:          defaultMaximumOrphanTransactionSize,
 	}
 }
diff --git a/domain/miningmanager/mempool/error.go b/domain/miningmanager/mempool/error.go
index bc51bb3a0..c86e97d41 100644
--- a/domain/miningmanager/mempool/error.go
+++ b/domain/miningmanager/mempool/error.go
@@ -39,32 +39,34 @@ type RejectCode uint8
 
 // These constants define the various supported reject codes.
 const (
-	RejectMalformed       RejectCode = 0x01
-	RejectInvalid         RejectCode = 0x10
-	RejectObsolete        RejectCode = 0x11
-	RejectDuplicate       RejectCode = 0x12
-	RejectNotRequested    RejectCode = 0x13
-	RejectNonstandard     RejectCode = 0x40
-	RejectDust            RejectCode = 0x41
-	RejectInsufficientFee RejectCode = 0x42
-	RejectFinality        RejectCode = 0x43
-	RejectDifficulty      RejectCode = 0x44
-	RejectImmatureSpend   RejectCode = 0x45
+	RejectMalformed          RejectCode = 0x01
+	RejectInvalid            RejectCode = 0x10
+	RejectObsolete           RejectCode = 0x11
+	RejectDuplicate          RejectCode = 0x12
+	RejectNotRequested       RejectCode = 0x13
+	RejectNonstandard        RejectCode = 0x40
+	RejectDust               RejectCode = 0x41
+	RejectInsufficientFee    RejectCode = 0x42
+	RejectFinality           RejectCode = 0x43
+	RejectDifficulty         RejectCode = 0x44
+	RejectImmatureSpend      RejectCode = 0x45
+	RejectIncompatibleOrphan RejectCode = 0x64
 )
 
 // Map of reject codes back strings for pretty printing.
 var rejectCodeStrings = map[RejectCode]string{
-	RejectMalformed:       "REJECT_MALFORMED",
-	RejectInvalid:         "REJECT_INVALID",
-	RejectObsolete:        "REJECT_OBSOLETE",
-	RejectDuplicate:       "REJECT_DUPLICATE",
-	RejectNonstandard:     "REJECT_NONSTANDARD",
-	RejectDust:            "REJECT_DUST",
-	RejectInsufficientFee: "REJECT_INSUFFICIENTFEE",
-	RejectFinality:        "REJECT_FINALITY",
-	RejectDifficulty:      "REJECT_DIFFICULTY",
-	RejectNotRequested:    "REJECT_NOTREQUESTED",
-	RejectImmatureSpend:   "REJECT_IMMATURESPEND",
+	RejectMalformed:          "REJECT_MALFORMED",
+	RejectInvalid:            "REJECT_INVALID",
+	RejectObsolete:           "REJECT_OBSOLETE",
+	RejectDuplicate:          "REJECT_DUPLICATE",
+	RejectNonstandard:        "REJECT_NON_STANDARD",
+	RejectDust:               "REJECT_DUST",
+	RejectInsufficientFee:    "REJECT_INSUFFICIENT_FEE",
+	RejectFinality:           "REJECT_FINALITY",
+	RejectDifficulty:         "REJECT_DIFFICULTY",
+	RejectNotRequested:       "REJECT_NOT_REQUESTED",
+	RejectImmatureSpend:      "REJECT_IMMATURE_SPEND",
+	RejectIncompatibleOrphan: "REJECT_INCOMPATIBLE_ORPHAN",
 }
 
 // String returns the RejectCode in human-readable form.
diff --git a/domain/miningmanager/mempool/orphan_pool.go b/domain/miningmanager/mempool/orphan_pool.go
index b97a82e7c..615676eb4 100644
--- a/domain/miningmanager/mempool/orphan_pool.go
+++ b/domain/miningmanager/mempool/orphan_pool.go
@@ -1,7 +1,10 @@
 package mempool
 
 import (
+	"fmt"
+
 	"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
+	"github.com/kaspanet/kaspad/domain/consensus/utils/estimatedsize"
 	"github.com/kaspanet/kaspad/domain/miningmanager/mempool/model"
 	"github.com/pkg/errors"
 )
@@ -25,10 +28,51 @@ func newOrphansPool(mp *mempool) *orphansPool {
 	}
 }
 
-func (op *orphansPool) maybeAddOrphan(transaction *externalapi.DomainTransaction,
-	missingParents []*externalapi.DomainTransactionID, isHighPriority bool) error {
+func (op *orphansPool) maybeAddOrphan(transaction *externalapi.DomainTransaction, isHighPriority bool) error {
+	serializedLength := estimatedsize.TransactionEstimatedSerializedSize(transaction)
+	if serializedLength > uint64(op.mempool.config.maximumOrphanTransactionSize) {
+		str := fmt.Sprintf("orphan transaction size of %d bytes is "+
+			"larger than max allowed size of %d bytes",
+			serializedLength, op.mempool.config.maximumOrphanTransactionSize)
+		return txRuleError(RejectIncompatibleOrphan, str)
+	}
+	if op.mempool.config.maximumOrphanTransactionSize <= 0 {
+		return nil
+	}
+	for len(op.allOrphans) >= op.mempool.config.maximumOrphanTransactionSize {
+		// Don't remove redeemers in the case of a random eviction since
+		// it is quite possible it might be needed again shortly.
+		err := op.removeOrphan(op.randomOrphan().TransactionID(), false)
+		if err != nil {
+			return err
+		}
+	}
 
-	panic("orphansPool.maybeAddOrphan not implemented") // TODO (Mike)
+	return op.addOrphan(transaction, isHighPriority)
+}
+
+func (op *orphansPool) addOrphan(transaction *externalapi.DomainTransaction, isHighPriority bool) error {
+	virtualDAAScore, err := op.mempool.virtualDAAScore()
+	if err != nil {
+		return err
+	}
+	orphanTransaction := &model.OrphanTransaction{
+		Transaction:     transaction,
+		IsHighPriority:  isHighPriority,
+		AddedAtDAAScore: virtualDAAScore,
+	}
+
+	op.allOrphans[*orphanTransaction.TransactionID()] = orphanTransaction
+	for _, input := range transaction.Inputs {
+		if input.UTXOEntry == nil {
+			if _, ok := op.orphansByPreviousOutpoint[input.PreviousOutpoint]; !ok {
+				op.orphansByPreviousOutpoint[input.PreviousOutpoint] = idToOrphan{}
+			}
+			op.orphansByPreviousOutpoint[input.PreviousOutpoint][*orphanTransaction.TransactionID()] = orphanTransaction
+		}
+	}
+
+	return nil
 }
 
 func (op *orphansPool) processOrphansAfterAcceptedTransaction(acceptedTransaction *model.MempoolTransaction) (
@@ -125,9 +169,7 @@ func (op *orphansPool) expireOrphanTransactions() error {
 
 		// Remove all transactions whose addedAtDAAScore is older then transactionExpireIntervalDAAScore
 		if virtualDAAScore-orphanTransaction.AddedAtDAAScore > op.mempool.config.orphanExpireIntervalDAAScore {
-			// Don't remove redeemers in the case of a random eviction since
-			// it is quite possible it might be needed again shortly.
-			err = op.removeOrphan(orphanTransaction.TransactionID(), false)
+			err = op.removeOrphan(orphanTransaction.TransactionID(), true)
 			if err != nil {
 				return err
 			}
@@ -137,3 +179,11 @@ func (op *orphansPool) expireOrphanTransactions() error {
 	op.lastExpireScan = virtualDAAScore
 	return nil
 }
+
+func (op *orphansPool) randomOrphan() *model.OrphanTransaction {
+	for _, orphan := range op.allOrphans {
+		return orphan
+	}
+
+	return nil
+}