diff --git a/internal/aws/kinesis/kinesis.go b/internal/aws/kinesis/kinesis.go
index 744dfef5..9c2531af 100644
--- a/internal/aws/kinesis/kinesis.go
+++ b/internal/aws/kinesis/kinesis.go
@@ -23,6 +23,7 @@ import (
 type Aggregate struct {
 	Record       *rec.AggregatedRecord
 	Count        int
+	Size         int
 	PartitionKey string
 }
 
@@ -31,11 +32,49 @@ type Aggregate struct {
 func (a *Aggregate) New() {
 	a.Record = &rec.AggregatedRecord{}
 	a.Count = 0
+	a.Size = 0
 
 	a.PartitionKey = ""
 	a.Record.PartitionKeyTable = make([]string, 0)
 }
 
+func varIntSize(i int) int {
+	if i == 0 {
+		return 1
+	}
+
+	var needed int
+	for i > 0 {
+		needed++
+		i >>= 1
+	}
+
+	bytes := needed / 7
+	if needed%7 > 0 {
+		bytes++
+	}
+
+	return bytes
+}
+
+func (a *Aggregate) calculateRecordSize(data []byte, partitionKey string) int {
+	var recordSize int
+	// https://github.com/awslabs/kinesis-aggregation/blob/398fbd4b430d4bf590431b301d03cbbc94279cef/python/aws_kinesis_agg/aggregator.py#L344-L349
+	pkSize := 1 + varIntSize(len(partitionKey)) + len(partitionKey)
+	recordSize += pkSize
+	// https://github.com/awslabs/kinesis-aggregation/blob/398fbd4b430d4bf590431b301d03cbbc94279cef/python/aws_kinesis_agg/aggregator.py#L362-L364
+	pkiSize := 1 + varIntSize(a.Count)
+	recordSize += pkiSize
+	// https://github.com/awslabs/kinesis-aggregation/blob/398fbd4b430d4bf590431b301d03cbbc94279cef/python/aws_kinesis_agg/aggregator.py#L371-L374
+	dataSize := 1 + varIntSize(len(data)) + len(data)
+	recordSize += dataSize
+	// https://github.com/awslabs/kinesis-aggregation/blob/398fbd4b430d4bf590431b301d03cbbc94279cef/python/aws_kinesis_agg/aggregator.py#L376-L378
+	recordSize = recordSize + 1 + varIntSize(pkiSize+dataSize)
+
+	// input record size + current aggregated record size + 4 byte magic header + 16 byte MD5 digest
+	return recordSize + a.Record.XXX_Size() + 20
+}
+
 // Add inserts a Kinesis record into an aggregated Kinesis record
 // https://github.com/awslabs/kinesis-aggregation/blob/398fbd4b430d4bf590431b301d03cbbc94279cef/python/aws_kinesis_agg/aggregator.py#L382
 func (a *Aggregate) Add(data []byte, partitionKey string) bool {
@@ -49,15 +88,25 @@ func (a *Aggregate) Add(data []byte, partitionKey string) bool {
 		a.PartitionKey = partitionKey
 	}
 
+	// Verify the record size won't exceed the 1 MB limit of the Kinesis service.
+	// https://docs.aws.amazon.com/streams/latest/dev/service-sizes-and-limits.html
+	if a.calculateRecordSize(data, partitionKey) > 1024*1024 {
+		return false
+	}
+
 	pki := uint64(a.Count)
 	r := &rec.Record{
 		PartitionKeyIndex: &pki,
 		Data:              data,
 	}
 
+	// Append the data to the aggregated record.
 	a.Record.Records = append(a.Record.Records, r)
 	a.Record.PartitionKeyTable = append(a.Record.PartitionKeyTable, partitionKey)
+
+	// Update the record count and size. This is not used in the aggregated record.
 	a.Count++
+	a.Size += a.calculateRecordSize(data, partitionKey)
 
 	return true
 }
diff --git a/transform/send_aws_kinesis_data_stream.go b/transform/send_aws_kinesis_data_stream.go
index d66d5b37..532ed0a1 100644
--- a/transform/send_aws_kinesis_data_stream.go
+++ b/transform/send_aws_kinesis_data_stream.go
@@ -203,6 +203,8 @@ func (tf *sendAWSKinesisDataStream) aggregateRecords(partitionKey string, data [
 		records = append(records, agg.Get())
 
 		agg.New()
+
+		// This silently drops any data that is between ~0.9999 MB and 1 MB.
 		_ = agg.Add(d, partitionKey)
 	}