diff --git a/src/cool_seq_tool/mappers/exon_genomic_coords.py b/src/cool_seq_tool/mappers/exon_genomic_coords.py
index 189ec38..1509cc3 100644
--- a/src/cool_seq_tool/mappers/exon_genomic_coords.py
+++ b/src/cool_seq_tool/mappers/exon_genomic_coords.py
@@ -865,6 +865,22 @@ async def _genomic_to_tx_segment(
         if use_alt_start_i and coordinate_type == CoordinateType.RESIDUE:
             genomic_pos = genomic_pos - 1  # Convert residue coordinate to inter-residue
 
+        # Validate that the breakpoint occurs within 150 bp of the first and last exon for the selected transcript.
+        # A breakpoint beyond this range is likely erroneous.
+        coordinate_check = await self._validate_genomic_breakpoint(
+            pos=genomic_pos, genomic_ac=genomic_ac, tx_ac=transcript
+        )
+        if not coordinate_check:
+            msg = (
+                f"{genomic_pos} on {genomic_ac} occurs more than 150 bp outside the "
+                f"exon boundaries of the {transcript} transcript, indicating this may not "
+                f"be a chimeric transcript junction and is unlikely to represent a "
+                f"contiguous coding sequence. Confirm that the genomic position "
+                f"{genomic_pos} is being used to represent transcript junction and not "
+                f"DNA breakpoint."
+            )
+            _logger.warning(msg)
+
         # Check if breakpoint occurs on an exon.
         # If not, determine the adjacent exon given the selected transcript
         if not self._is_exonic_breakpoint(genomic_pos, tx_exons):
@@ -932,6 +948,37 @@ async def _get_grch38_pos(
         )
         return liftover_data[1] if liftover_data else None
 
+    async def _validate_genomic_breakpoint(
+        self,
+        pos: int,
+        genomic_ac: str,
+        tx_ac: str,
+    ) -> bool:
+        """Validate that a genomic coordinate falls within the first and last exon
+            for a transcript on a given accession
+
+        :param pos: Genomic position on ``genomic_ac``
+        :param genomic_ac: RefSeq genomic accession, e.g. ``"NC_000007.14"``
+        :param transcript: A transcript accession
+        :return: ``True`` if the coordinate falls within 150bp of the first and last exon
+            for the transcript, ``False`` if not. Breakpoints past this threshold
+            are likely erroneous.
+        """
+        query = f"""
+            WITH tx_boundaries AS (
+                SELECT
+                MIN(alt_start_i) AS min_start,
+                MAX(alt_end_i) AS max_end
+                FROM {self.uta_db.schema}.tx_exon_aln_v
+                WHERE tx_ac = '{tx_ac}'
+                AND alt_ac = '{genomic_ac}'
+            )
+            SELECT * FROM tx_boundaries
+            WHERE {pos} between (tx_boundaries.min_start - 150) and (tx_boundaries.max_end + 150)
+            """  # noqa: S608
+        results = await self.uta_db.execute_query(query)
+        return bool(results)
+
     async def _get_tx_ac_gene(
         self,
         tx_ac: str,
diff --git a/tests/mappers/test_exon_genomic_coords.py b/tests/mappers/test_exon_genomic_coords.py
index 114f3e1..8a3ce10 100644
--- a/tests/mappers/test_exon_genomic_coords.py
+++ b/tests/mappers/test_exon_genomic_coords.py
@@ -1,5 +1,6 @@
 """Module for testing that Cool Seq Tool works correctly."""
 
+import logging
 from datetime import datetime
 
 import pytest
@@ -1463,7 +1464,7 @@ async def test_valid_inputs(test_egc_mapper, eln_grch38_intronic):
 
 
 @pytest.mark.asyncio
-async def test_invalid(test_egc_mapper):
+async def test_invalid(test_egc_mapper, caplog):
     """Test that invalid queries return `None`."""
     resp = await test_egc_mapper.genomic_to_tx_segment(
         transcript="NM_152263 3",
@@ -1514,6 +1515,37 @@ async def test_invalid(test_egc_mapper):
     genomic_tx_seg_service_checks(resp, is_valid=False)
     assert resp.errors == ["Must provide either `gene` or `transcript`"]
 
+    # Check 150 bp warning statement
+    with caplog.at_level(logging.WARNING):
+        await test_egc_mapper.genomic_to_tx_segment(
+            genomic_ac="NC_000001.11",
+            seg_start_genomic=9999999999998,
+            seg_end_genomic=9999999999999,
+            transcript="NM_152263.3",
+        )
+    assert any(
+        (
+            "9999999999998 on NC_000001.11 occurs more than 150 bp outside the exon "
+            "boundaries of the NM_152263.3 transcript, indicating this may not be "
+            "a chimeric transcript junction and is unlikely to represent a "
+            "contiguous coding sequence. Confirm that the genomic position 9999999999998 is "
+            "being used to represent transcript junction and not DNA breakpoint."
+        )
+        in record.message
+        for record in caplog.records
+    )
+    assert any(
+        (
+            "9999999999999 on NC_000001.11 occurs more than 150 bp outside the exon "
+            "boundaries of the NM_152263.3 transcript, indicating this may not be "
+            "a chimeric transcript junction and is unlikely to represent a "
+            "contiguous coding sequence. Confirm that the genomic position 9999999999999 is "
+            "being used to represent transcript junction and not DNA breakpoint."
+        )
+        in record.message
+        for record in caplog.records
+    )
+
     # Exon 22 does not exist
     resp = await test_egc_mapper.tx_segment_to_genomic(
         exon_start=None,