Over the last three decades, an increasing interest in the preparation of new materials for wound healing has been observed. Collagen is a widely used biomaterial, and especially fish skin collagen is more and more popular among scientists. This study aimed to obtain thin films from native fish skin collagen and collagen cross-linked with tannic acid. Infrared spectroscopy, mechanical test, topographic imaging, and swelling test were used to characterize the features of the mentioned films. Statistical evaluation of the results was conducted with the Q-Dixon test. Infrared spectroscopy analysis showed that in the IR spectra of examined biomaterials, there are slight shifts in band positions after tannic acid cross-linking. The mechanical properties of the cross-linked material were different from those of the native collagen film. The Young’s modulus was higher for cross-linked collagen, whereas the elongation at break was lower than for pure collagen. The swelling of the collagen films increased after cross-linking with tannic acid. Swelling tests indicated that collagen cross-linked with tannic acid absorbs more water than before cross-linking. The properties of collagen films were significantly improved after tannic acid cross-linking. All alterations can be a result of collagen cross-linking by tannic acid, probably by forming hydrogen bonds between collagen and tannic acid.