diff --git a/cmr/queries.py b/cmr/queries.py
index cdf9f2e..3e1c33a 100644
--- a/cmr/queries.py
+++ b/cmr/queries.py
@@ -39,6 +39,25 @@
 PointLike: TypeAlias = Tuple[FloatLike, FloatLike]
 
 
+def _format_float(value: Union[float, int, str]) -> str:
+    """Format a number as a plain decimal string, never using scientific notation.
+
+    Python's default str() switches to scientific notation for floats outside
+    roughly [1e-4, 1e16), e.g. ``1e-05`` for ``0.00001``.  CMR rejects
+    scientific notation in URL parameters with "is not a valid URL encoded point".
+
+    Integers and strings are returned as-is (``str(1000)`` → ``"1000"``).
+    Floats use their natural str() representation (``str(1.0)`` → ``"1.0"``)
+    unless that produces scientific notation, in which case a fixed-point
+    decimal is returned instead.
+    """
+    s = str(value)
+    if "e" not in s and "E" not in s:
+        return s
+    # Scientific notation detected: convert to plain decimal, strip trailing zeros
+    return f"{float(value):.15f}".rstrip("0").rstrip(".")
+
+
 class Query:
     """
     Base class for all CMR queries.
@@ -618,7 +637,7 @@ def point(self, lon: FloatLike, lat: FloatLike) -> Self:
         if "point" not in self.params:
             self.params["point"] = []
 
-        self.params["point"].append(f"{lon},{lat}")
+        self.params["point"].append(f"{_format_float(lon)},{_format_float(lat)}")
 
         return self
 
@@ -630,7 +649,7 @@ def circle(self, lon: FloatLike, lat: FloatLike, dist: FloatLike) -> Self:
         :param dist: distance in meters around waypoint (lat,lon)
         :returns: self
         """
-        self.params['circle'] = f"{lon},{lat},{dist}"
+        self.params['circle'] = f"{_format_float(lon)},{_format_float(lat)},{_format_float(dist)}"
 
         return self
 
@@ -672,7 +691,7 @@ def polygon(self, coordinates: Sequence[PointLike]) -> Self:
             )
 
         # convert to strings
-        as_strs = [str(val) for val in as_floats]
+        as_strs = [_format_float(val) for val in as_floats]
 
         self.params["polygon"] = ",".join(as_strs)
 
@@ -697,7 +716,8 @@ def bounding_box(
         """
 
         self.params["bounding_box"] = (
-            f"{float(lower_left_lon)},{float(lower_left_lat)},{float(upper_right_lon)},{float(upper_right_lat)}"
+            f"{_format_float(float(lower_left_lon))},{_format_float(float(lower_left_lat))},"
+            f"{_format_float(float(upper_right_lon))},{_format_float(float(upper_right_lat))}"
         )
 
         return self
@@ -734,7 +754,7 @@ def line(self, coordinates: Sequence[PointLike]) -> Self:
             as_floats.extend([float(lon), float(lat)])
 
         # cast back to string for join
-        as_strs = [str(val) for val in as_floats]
+        as_strs = [_format_float(val) for val in as_floats]
 
         self.params["line"] = ",".join(as_strs)
 
diff --git a/tests/test_granule.py b/tests/test_granule.py
index fbf188f..1f702a5 100644
--- a/tests/test_granule.py
+++ b/tests/test_granule.py
@@ -427,6 +427,34 @@ def test_line_set(self):
         query.line([("1", 1.1), (2, 2)])
         self.assertEqual(query.params["line"], "1.0,1.1,2.0,2.0")
 
+    def test_point_no_scientific_notation(self):
+        query = GranuleQuery()
+        query.point(1e-5, 1e-8)
+        self.assertEqual(query.params["point"], ["0.00001,0.00000001"])
+
+    def test_circle_no_scientific_notation(self):
+        query = GranuleQuery()
+        query.circle(1e-5, 1e-8, 1000)
+        self.assertEqual(query.params["circle"], "0.00001,0.00000001,1000")
+
+    def test_bounding_box_no_scientific_notation(self):
+        query = GranuleQuery()
+        query.bounding_box(1e-5, 1e-8, 1e-4, 1e-7)
+        self.assertEqual(query.params["bounding_box"], "0.00001,0.00000001,0.0001,0.0000001")
+
+    def test_polygon_no_scientific_notation(self):
+        query = GranuleQuery()
+        query.polygon([(1e-5, 1e-8), (1e-4, 1e-8), (1e-4, 1e-7), (1e-5, 1e-8)])
+        self.assertEqual(
+            query.params["polygon"],
+            "0.00001,0.00000001,0.0001,0.00000001,0.0001,0.0000001,0.00001,0.00000001",
+        )
+
+    def test_line_no_scientific_notation(self):
+        query = GranuleQuery()
+        query.line([(1e-5, 1e-8), (1e-4, 1e-7)])
+        self.assertEqual(query.params["line"], "0.00001,0.00000001,0.0001,0.0000001")
+
     def test_invalid_spatial_state(self):
         query = GranuleQuery()
 
diff --git a/tests/test_queries.py b/tests/test_queries.py
index 142a026..21739e5 100644
--- a/tests/test_queries.py
+++ b/tests/test_queries.py
@@ -1,4 +1,7 @@
+import pytest
+
 from cmr import Query
+from cmr.queries import _format_float
 
 
 class MockQuery(Query):
@@ -55,3 +58,17 @@ def test_token_replaces_existing_auth_header():
     query.token("token")
 
     assert query.headers["Authorization"] == "token"
+
+
+@pytest.mark.parametrize("value,expected", [
+    (1.5,    "1.5"),       # normal float — no change
+    (10,     "10"),        # integer — no change
+    ("1.5",  "1.5"),       # string — passed through as-is
+    (0.0,    "0.0"),       # zero — no scientific notation
+    (1e-5,   "0.00001"),   # small float Python renders as "1e-05"
+    (1e-8,   "0.00000001"),
+    (-1e-5,  "-0.00001"),  # negative scientific notation
+    (1.23e-5, "0.0000123"),
+])
+def test_format_float(value, expected):
+    assert _format_float(value) == expected