The roles of drilling fluids are numerous in the drilling operations, where the control of filtration and rheological properties is of key importance. Additives are added to drilling fluids to improve properties. Waste in oil industry must be disposed of properly, and additives as part of the drilling fluids are often harmful to the environment. Nowadays, numerous researches are being carried out in order to implement biodegradable additives in the oil industry. In this paper, drilling fluids were examined in which tangerine peel powder with a particle size of up to 0,1 mm was used as an additive. In two basic water-based drilling fluids, with a complex composition, mandarin peel powder was added as an additive in different concentrations. By gradually changing the concentration of carboxymethylcellulose as the main additive for controling filtration properties and adding mandarin peel powder as a substitution for carboxymethylcellulose, drilling fluids were obtained whose properties were subjected to tests. The results showed that the addition of mandarin peel powder as an additive in combination with carboxymethylcellulose reduces filtration, while adding 15 g of mandarin peel powder in basic drilling fluid A, in which the concentration of carboxymethylcellulose is 5 g/L, results in a decrease in filtrate volume by as much as 29 % compared to basic drilling fluid A. Adding 30 g/L of mandarin peel powder to basic drilling fluid B (of a different composition with a concentration of carboxymethylcellulose 2 g/L) also resultrs in a 29 % decrease in the filtrate volume compared to basic drilling fluid B, but significant changes in rheological properties also occur. It was concluded that mandarin peel powder in different concentrations affects the rheological and filtration properties of the complex drilling fluids, and the best results are visible when combining the standard carboxymethylcellulose filtration control additive in a concentration of 5 g/L and the optimal concentration of mandarin peel powder with particle size up to 0.1 mm of 15 g/L. Mandarin peel powder, with additional tests, has a future as a drilling fluid additive in the oil industry.