diff --git a/Doc/library/csv.rst b/Doc/library/csv.rst
index 64baa69be4af31..afaf464dbcf420 100644
--- a/Doc/library/csv.rst
+++ b/Doc/library/csv.rst
@@ -295,6 +295,11 @@ The :mod:`csv` module defines the following classes:
       Twenty rows after the first row are sampled; if more than half of columns +
       rows meet the criteria, :const:`True` is returned.
 
+      Additionally, if all columns are found to be strings and have varying
+      lengths, the average length of all the strings becomes a crucial factor
+      in the determination process.
+
+
    .. note::
 
       This method is a rough heuristic and may produce both false positives and
diff --git a/Lib/csv.py b/Lib/csv.py
index 77f30c8d2b1f61..e58160569e91fa 100644
--- a/Lib/csv.py
+++ b/Lib/csv.py
@@ -394,6 +394,8 @@ def has_header(self, sample):
         # can't be determined, it is assumed to be a string in which case
         # the length of the string is the determining factor: if all of the
         # rows except for the first are the same length, it's a header.
+        # When the strings have varying length, the average length of all
+        # strings becomes a determining factor.
         # Finally, a 'vote' is taken at the end for each column, adding or
         # subtracting from the likelihood of the first row being a header.
 
@@ -402,8 +404,9 @@ def has_header(self, sample):
         header = next(rdr) # assume first row is header
 
         columns = len(header)
-        columnTypes = {}
-        for i in range(columns): columnTypes[i] = None
+        columnTypes = {i: None for i in range(columns)}
+        average_size = 0
+        col_are_strings = True
 
         checked = 0
         for row in rdr:
@@ -416,6 +419,10 @@ def has_header(self, sample):
                 continue # skip rows that have irregular number of columns
 
             for col in list(columnTypes.keys()):
+                # check if all col are strings
+                if row[col].isnumeric():
+                    col_are_strings = False
+
                 thisType = complex
                 try:
                     thisType(row[col])
@@ -426,6 +433,7 @@ def has_header(self, sample):
                 if thisType != columnTypes[col]:
                     if columnTypes[col] is None: # add new column type
                         columnTypes[col] = thisType
+                        average_size += len(row[col])
                     else:
                         # type is inconsistent, remove column from
                         # consideration
@@ -434,6 +442,13 @@ def has_header(self, sample):
         # finally, compare results against first row and "vote"
         # on whether it's a header
         hasHeader = 0
+
+        # special case when all columns are strings and columnTypes has been emptied
+        if not columnTypes and col_are_strings and columns > 0:
+            # If there are only columns of strings and no column types specified,
+            # update the dictionary to store the average length of all strings
+            columnTypes[0] = average_size // columns
+
         for col, colType in columnTypes.items():
             if isinstance(colType, int): # it's a length
                 if len(header[col]) != colType:
diff --git a/Lib/test/test_csv.py b/Lib/test/test_csv.py
index 6a4180e6d1b0a1..c238fdd4851449 100644
--- a/Lib/test/test_csv.py
+++ b/Lib/test/test_csv.py
@@ -1188,6 +1188,18 @@ class TestSniffer(unittest.TestCase):
 abc\0def
 ghijkl\0mno
 ghi\0jkl
+"""
+    sample15 = """\
+sample,fastq_1,fastq_2
+A1-35-8,/mnt/scratch/sarek/data/A1-35-8/A1-35-8_R1.fastq.gz,/mnt/scratch/sarek/data/A1-35-8/A1-35-8_R2.fastq.gz
+A2-102-5,/mnt/scratch/sarek/data/A2-102-5/A2-102-5_R1.fastq.gz,/mnt/scratch/sarek/data/A2-102-5/A2-102-5_R2.fastq.gz
+A5-35-17,/mnt/scratch/sarek/data/A5-35-17/A5-35-17_R1.fastq.gz,/mnt/scratch/sarek/data/A5-35-17/A5-35-17_R2.fastq.gz
+AD1-7a,/mnt/scratch/sarek/data/AD1-7a/AD1-7a_R1.fastq.gz,/mnt/scratch/sarek/data/AD1-7a/AD1-7a_R2.fastq.gz
+AD1-83a,/mnt/scratch/sarek/data/AD1-83a/AD1-83a_R1.fastq.gz,/mnt/scratch/sarek/data/AD1-83a/AD1-83a_R2.fastq.gz
+AD2-60a,/mnt/scratch/sarek/data/AD2-60a/AD2-60a_R1.fastq.gz,/mnt/scratch/sarek/data/AD2-60a/AD2-60a_R2.fastq.gz
+Arg1366,/mnt/scratch/sarek/data/Arg1366/Arg1366_R1.fastq.gz,/mnt/scratch/sarek/data/Arg1366/Arg1366_R2.fastq.gz
+Br795,/mnt/scratch/sarek/data/Br795/Br795_R1.fastq.gz,/mnt/scratch/sarek/data/Br795/Br795_R2.fastq.gz
+Bt100,/mnt/scratch/sarek/data/Bt100/Bt100_R1.fastq.gz,/mnt/scratch/sarek/data/Bt100/Bt100_R2.fastq.gz
 """
 
     def test_issue43625(self):
@@ -1200,6 +1212,7 @@ def test_has_header_strings(self):
         sniffer = csv.Sniffer()
         self.assertFalse(sniffer.has_header(self.sample10))
         self.assertFalse(sniffer.has_header(self.sample11))
+        self.assertTrue(sniffer.has_header(self.sample15))
 
     def test_has_header(self):
         sniffer = csv.Sniffer()
diff --git a/Misc/NEWS.d/next/Library/2023-05-01-18-53-20.gh-issue-102140._4gFLu.rst b/Misc/NEWS.d/next/Library/2023-05-01-18-53-20.gh-issue-102140._4gFLu.rst
new file mode 100644
index 00000000000000..88e89d9fcf943d
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2023-05-01-18-53-20.gh-issue-102140._4gFLu.rst
@@ -0,0 +1 @@
+Fix false negatives in the :meth:`~csv.Sniffer.has_header` method of :class:`csv.Sniffer` when all cells in the first row are strings.