The new solid solutions BaMn_1-xZn_xF₄ have been investigated by different experimental methods in the temperature range 10 K-300 K. X-ray and calorimetric measurements show that the incommensurate phase characteristic of BaMnF₄ is also observed for x ≤ 0.25. Raman spectra were obtained for BaMn_0.5Zn_0.5F₄ and BaMn_0.25Zn_0.75F₄. Two low-frequency, temperature-dependent bands were observed over the whole temperature range investigated. These results are discussed in connection with structural disorder and the presence of precursor effects of an incommensurate phase transition.