The systematic studies of both magnetic and magnetotransport properties of Zn0.947Mn0.053GeAs2 diluted magnetic semiconductor are presented. The paramagnetic behaviour of the sample confirms that the solubility of Mn in the studied alloy is of the order of 5 at%. The Curie-Weiss behaviour of magnetic susceptibility is preserved only at low temperatures, T < 100K indicating the presence of short-range magnetic interactions in the system due to the presence of groups of Mn counting few ions. The high-field magnetization together with magneto-resistance data is used to estimate the amount of magnetic ions active in the semiconductor matrix. The obtained results showed that the amount of magnetically active Mn ions in the semiconductors matrix is two orders of magnitude lower than the value obtained from X-ray fluorescence measurements. The magnetotransport studies revealed that only about 30% of all Mn ions are electrically active in the semiconductor matrix. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim