diff --git a/pygmt/src/grdfill.py b/pygmt/src/grdfill.py
index 1492e1e9c73..40818a8f4d5 100644
--- a/pygmt/src/grdfill.py
+++ b/pygmt/src/grdfill.py
@@ -2,7 +2,6 @@
 grdfill - Interpolate across holes in a grid.
 """
 
-import warnings
 from collections.abc import Sequence
 from typing import Literal
 
@@ -23,14 +22,12 @@ def _validate_params(
     neighbor_fill=None,
     spline_fill=None,
     inquire=False,
-    mode=None,
 ):
     """
     Validate the fill/inquire parameters.
 
     >>> _validate_params(constant_fill=20.0)
     >>> _validate_params(inquire=True)
-    >>> _validate_params(mode="c20.0")
     >>> _validate_params(constant_fill=20.0, grid_fill="bggrid.nc")
     Traceback (most recent call last):
     ...
@@ -45,13 +42,6 @@ def _validate_params(
     pygmt.exceptions.GMTInvalidInput: Need to specify parameter ...
     """
     _fill_params = "'constant_fill'/'grid_fill'/'neighbor_fill'/'spline_fill'"
-    # The deprecated 'mode' parameter is given.
-    if mode is not None:
-        msg = (
-            "The 'mode' parameter is deprecated since v0.15.0 and will be removed in "
-            f"v0.19.0. Use {_fill_params} instead."
-        )
-        warnings.warn(msg, FutureWarning, stacklevel=2)
 
     n_given = sum(
         param is not None and param is not False
@@ -61,11 +51,10 @@ def _validate_params(
             neighbor_fill,
             spline_fill,
             inquire,
-            mode,
         ]
     )
     if n_given > 1:  # More than one mutually exclusive parameter is given.
-        msg = f"Parameters {_fill_params}/'inquire'/'mode' are mutually exclusive."
+        msg = f"Parameters {_fill_params}/'inquire' are mutually exclusive."
         raise GMTInvalidInput(msg)
     if n_given == 0:  # No parameters are given.
         msg = (
@@ -76,7 +65,6 @@ def _validate_params(
 
 
 @fmt_docstring
-# TODO(PyGMT>=0.19.0): Remove the deprecated 'mode' parameter.
 # TODO(PyGMT>=0.20.0): Remove the deprecated '*fill' parameters.
 @deprecate_parameter(
     "constantfill", "constant_fill", "v0.18.0", remove_version="v0.20.0"
@@ -87,7 +75,7 @@ def _validate_params(
 )
 @deprecate_parameter("splinefill", "spline_fill", "v0.18.0", remove_version="v0.20.0")
 @use_alias(f="coltypes")
-def grdfill(  # noqa: PLR0913
+def grdfill(
     grid: PathLike | xr.DataArray,
     outgrid: PathLike | None = None,
     constant_fill: float | None = None,
@@ -96,7 +84,6 @@ def grdfill(  # noqa: PLR0913
     spline_fill: float | bool | None = None,
     inquire: bool = False,
     hole: float | None = None,
-    mode: str | None = None,
     region: Sequence[float | str] | str | None = None,
     verbose: Literal["quiet", "error", "warning", "timing", "info", "compat", "debug"]
     | bool = False,
@@ -147,16 +134,6 @@ def grdfill(  # noqa: PLR0913
         Output the bounds of each hole. The bounds are returned as a 2-D numpy array in
         the form of (west, east, south, north). No grid fill takes place and ``outgrid``
         is ignored.
-    mode
-        Specify the hole-filling algorithm to use. Choose from **c** for constant fill
-        and append the constant value, **n** for nearest neighbor (and optionally append
-        a search radius in pixels [default radius is :math:`r^2 = \sqrt{ X^2 + Y^2 }`,
-        where (*X,Y*) are the node dimensions of the grid]), or **s** for bicubic spline
-        (optionally append a *tension* parameter [Default is no tension]).
-
-        .. deprecated:: 0.15.0
-            Use ``constant_fill``, ``grid_fill``, ``neighbor_fill``, or ``spline_fill``
-            instead. The parameter will be removed in v0.19.0.
 
     $region
     $coltypes
@@ -189,13 +166,10 @@ def grdfill(  # noqa: PLR0913
            [6.16666667, 7.83333333, 0.5       , 2.5       ]])
     """
     # Validate the fill/inquire parameters.
-    _validate_params(
-        constant_fill, grid_fill, neighbor_fill, spline_fill, inquire, mode
-    )
+    _validate_params(constant_fill, grid_fill, neighbor_fill, spline_fill, inquire)
 
     # _validate_params has already ensured that only one of the parameters is set.
     aliasdict = AliasSystem(
-        A=Alias(mode, name="mode"),
         Ac=Alias(constant_fill, name="constant_fill"),
         # For grid_fill, append the actual or virtual grid file name later.
         Ag=Alias(grid_fill is not None, name="grid_fill"),
diff --git a/pygmt/tests/test_grdfill.py b/pygmt/tests/test_grdfill.py
index 16788229f86..29a654e38f0 100644
--- a/pygmt/tests/test_grdfill.py
+++ b/pygmt/tests/test_grdfill.py
@@ -156,13 +156,3 @@ def test_grdfill_inquire_and_fill(grid):
     """
     with pytest.raises(GMTInvalidInput):
         grdfill(grid=grid, inquire=True, constant_fill=20)
-
-
-# TODO(PyGMT>=0.19.0): Remove this test.
-def test_grdfill_deprecated_mode(grid, expected_grid):
-    """
-    Test that grdfill fails with deprecated `mode` argument.
-    """
-    with pytest.warns(FutureWarning):
-        result = grdfill(grid=grid, mode="c20")
-    xr.testing.assert_allclose(a=result, b=expected_grid)