Mixed martial arts (MMA) athletes must achieve high strength levels to face the physical demands of an MMA fight. This study compared MMA athletes' maximal isometric and dynamic strength according to the competitive level and weight class. Twenty-one male MMA athletes were divided into lightweight professional (LWP; = 9), lightweight elite (LWE; = 4), heavyweight professional (HWP; = 4), and heavyweight elite (HWE; = 4). The handgrip and isometric lumbar strength tests assessed the isometric strength, and the one-repetition maximum (1RM) bench press and 4RM leg press the dynamic strength. Univariate ANOVA showed differences between groups in absolute and relative 1RM bench press and absolute isometric lumbar strength. Post hoc tests showed differences in 1RM bench press between HWE and LWE (117.0 ± 17.8 kg vs. 81.0 ± 10.0 kg) and HWE and LWP athletes (117.0 ± 17.8 kg vs. 76.7 ± 13.7 kg; 1.5 ± 0.2 kg·BW vs. 1.1 ± 0.2 kg·BW). In addition, there was a correlation between 1RM bench press and isometric lumbar strength for absolute ( = 0.67) and relative values ( = 0.50). This study showed that the 1RM bench press and isometric lumbar strength were associated and could differentiate MMA athletes according to their competitive level and weight class. Therefore, optimizing the force production in the upper body and lower back seems important in elite and professional MMA athletes.