<p>Distribution, behavior, predator-prey relationship, and population dynamics of phytoseiid and tetranychid mites in agricultural and natural landscapes are important for understanding the potential use of beneficial mites in biological control. The population dynamics of <i>Tetranychus urticae</i> Koch, 1836 (Acari: Tetranychidae) and its predator <i>Euseius finlandicus</i> (Oudemans, 1915) (Acari: Phytoseiidae) on bean (<i>Phaseolus vulgaris</i> L., Fabaceae) were monitored under field conditions. The population dynamics and seasonal densities of prey and predator mites were investigated for two years. While the highest densities of eggs, larvae, nymphs, female, and male adults were 49.95, 5.33, 8.97, 5.77, and 1.60/leaf, respectively recorded at 9th week in 2019 for all life stages of <i>T. urticae</i>, this ratio was observed as 116, 35.22, 41.65, 32.52, and 12.82/leaf, respectively at 12th week in 2020. The density of <i>Euseius filandicus</i> associated with <i>T. urticae</i> reached the highest rate of 0.83 mites/leaf at 7th week in 2019 and 0.62 mites/leaf at 8th week in 2020. Correlation between <i>E. finlandicus</i> and <i>T. urticae</i> by using Sorensen coefficient (Iia) was calculated as 0.52 in 2019 and 0.97 in 2020. The results of the current study revealed a compelling relationship between the prey and the predator mites according to Sorensen’s coefficient (Iia). It is concluded that the densities of the prey and the predator mites were compatible during both years of the study. The populations of prey and predator mites were observed to be comparable for the first time in Ankara’s Cubuk district in Türkiye.</p>