diff --git a/docs/release_notes/next/fix-2397-fix-fits_file_support b/docs/release_notes/next/fix-2397-fix-fits_file_support
new file mode 100644
index 00000000000..fc29add799d
--- /dev/null
+++ b/docs/release_notes/next/fix-2397-fix-fits_file_support
@@ -0,0 +1 @@
+#2397: Fix FITS file support for drag and drop functionality within Mantid Imaging. This fix also resolves FITS file support when launching Mantid Imaging via the CLI with the `--path` optional argument.
diff --git a/mantidimaging/core/io/loader/loader.py b/mantidimaging/core/io/loader/loader.py
index e78fa99e69d..adedf8a1e1e 100644
--- a/mantidimaging/core/io/loader/loader.py
+++ b/mantidimaging/core/io/loader/loader.py
@@ -67,7 +67,9 @@ def _fitsread(filename: Path | str) -> np.ndarray:
         raise RuntimeError(f"Could not load at least one FITS image/table file from: {filename}")
 
     # get the image data
-    return image[0].data
+    image_data = image[0].data
+    image.close(filename)
+    return image_data
 
 
 def _imread(filename: Path | str) -> np.ndarray:
diff --git a/mantidimaging/core/io/utility.py b/mantidimaging/core/io/utility.py
index 5bbe702427d..ca2c8a05ff5 100644
--- a/mantidimaging/core/io/utility.py
+++ b/mantidimaging/core/io/utility.py
@@ -10,18 +10,24 @@
 log = getLogger(__name__)
 
 DEFAULT_IO_FILE_FORMAT = 'tif'
-NEXUS_PROCESSED_DATA_PATH = "processed-data"
+NEXUS_PROCESSED_DATA_PATH = 'processed-data'
 
 THRESHOLD_180 = np.radians(1)
 
 
 def find_first_file_that_is_possibly_a_sample(file_path: str) -> str | None:
-    # Grab all .tif or .tiff files
-    possible_files = glob.glob(os.path.join(file_path, "**/*.tif*"), recursive=True)
-
+    """
+    Finds the first file that is possibly a tif, .tiff, .fit or .fits sample file.
+    If files are found, the files are sorted and filtered based on name and returned.
+    """
+    file_types = ['tif', 'tiff', 'fit', 'fits']
+    for file_type in file_types:
+        possible_files = glob.glob(os.path.join(file_path, f'**/*.{file_type}'), recursive=True)
+        if possible_files:
+            break
     for possible_file in sorted(possible_files):
         lower_filename = os.path.basename(possible_file).lower()
-        if "flat" not in lower_filename and "dark" not in lower_filename and "180" not in lower_filename:
+        if 'flat' not in lower_filename and 'dark' not in lower_filename and '180' not in lower_filename:
             return possible_file
     return None