@@ -446,6 +446,7 @@ Reshaping
 ^^^^^^^^^
 - Bug in :func:`crosstab` when ``dropna=False`` would not keep ``np.nan`` in the result (:issue:`10772`)
 - Bug in :func:`merge_asof` raising ``KeyError`` for extension dtypes (:issue:`52904`)
+- Bug in :func:`merge_asof` raising ``ValueError`` for data backed by read-only ndarrays (:issue:`53513`)
 - Bug in :meth:`DataFrame.agg` and :meth:`Series.agg` on non-unique columns would return incorrect type when dist-like argument passed in (:issue:`51099`)
 - Bug in :meth:`DataFrame.idxmin` and :meth:`DataFrame.idxmax`, where the axis dtype would be lost for empty frames (:issue:`53265`)
 - Bug in :meth:`DataFrame.merge` not merging correctly when having ``MultiIndex`` with single level (:issue:`52331`)

@@ -50,28 +50,28 @@ def outer_join_indexer(
 npt.NDArray[np.intp],
 ]: ...
 def asof_join_backward_on_X_by_Y(
-left_values: np.ndarray, # asof_t[:]
-right_values: np.ndarray, # asof_t[:]
-left_by_values: np.ndarray, # by_t[:]
-right_by_values: np.ndarray, # by_t[:]
+left_values: np.ndarray, # ndarray[numeric_t]
+right_values: np.ndarray, # ndarray[numeric_t]
+left_by_values: np.ndarray, # ndarray[by_t]
+right_by_values: np.ndarray, # ndarray[by_t]
 allow_exact_matches: bool = ...,
 tolerance: np.number | float | None = ...,
 use_hashtable: bool = ...,
 ) -> tuple[npt.NDArray[np.intp], npt.NDArray[np.intp]]: ...
 def asof_join_forward_on_X_by_Y(
-left_values: np.ndarray, # asof_t[:]
-right_values: np.ndarray, # asof_t[:]
-left_by_values: np.ndarray, # by_t[:]
-right_by_values: np.ndarray, # by_t[:]
+left_values: np.ndarray, # ndarray[numeric_t]
+right_values: np.ndarray, # ndarray[numeric_t]
+left_by_values: np.ndarray, # ndarray[by_t]
+right_by_values: np.ndarray, # ndarray[by_t]
 allow_exact_matches: bool = ...,
 tolerance: np.number | float | None = ...,
 use_hashtable: bool = ...,
 ) -> tuple[npt.NDArray[np.intp], npt.NDArray[np.intp]]: ...
 def asof_join_nearest_on_X_by_Y(
-left_values: np.ndarray, # asof_t[:]
-right_values: np.ndarray, # asof_t[:]
-left_by_values: np.ndarray, # by_t[:]
-right_by_values: np.ndarray, # by_t[:]
+left_values: np.ndarray, # ndarray[numeric_t]
+right_values: np.ndarray, # ndarray[numeric_t]
+left_by_values: np.ndarray, # ndarray[by_t]
+right_by_values: np.ndarray, # ndarray[by_t]
 allow_exact_matches: bool = ...,
 tolerance: np.number | float | None = ...,
 use_hashtable: bool = ...,

@@ -679,10 +679,10 @@ ctypedef fused by_t:
 uint64_t
 
 
-def asof_join_backward_on_X_by_Y(numeric_t[:] left_values,
-numeric_t[:] right_values,
-by_t[:] left_by_values,
-by_t[:] right_by_values,
+def asof_join_backward_on_X_by_Y(ndarray[numeric_t] left_values,
+ndarray[numeric_t] right_values,
+ndarray[by_t] left_by_values,
+ndarray[by_t] right_by_values,
 bint allow_exact_matches=True,
 tolerance=None,
 bint use_hashtable=True):
@@ -756,10 +756,10 @@ def asof_join_backward_on_X_by_Y(numeric_t[:] left_values,
 return left_indexer, right_indexer
 
 
-def asof_join_forward_on_X_by_Y(numeric_t[:] left_values,
-numeric_t[:] right_values,
-by_t[:] left_by_values,
-by_t[:] right_by_values,
+def asof_join_forward_on_X_by_Y(ndarray[numeric_t] left_values,
+ndarray[numeric_t] right_values,
+ndarray[by_t] left_by_values,
+ndarray[by_t] right_by_values,
 bint allow_exact_matches=1,
 tolerance=None,
 bint use_hashtable=True):

@@ -2142,13 +2142,13 @@ def injection(obj):
 # we've verified above that no nulls exist
 left_values = left_values._data
 elif isinstance(left_values, ExtensionArray):
-left_values = np.array(left_values)
+left_values = left_values.to_numpy()
 
 if isinstance(right_values, BaseMaskedArray):
 # we've verified above that no nulls exist
 right_values = right_values._data
 elif isinstance(right_values, ExtensionArray):
-right_values = np.array(right_values)
+right_values = right_values.to_numpy()
 
 # a "by" parameter requires special handling
 if self.left_by is not None: