The study examined the effects of thick-bar resistance training (RT) using Fat Gripz™ (FG) attachments on upper-body and handgrip strength in active males who have had a minimum of three sessions of RT for at least one year. Twenty male participants were divided into two groups using FG (n = 10; age: 21.60 ± 1.64 y; weight: 74.06 ± 9.62 kg; height: 1.74 ± 0.33 m; RT experience: 2.80 ± 1.40 y) and the traditional bar without FG (NFG, n = 10; age: 21.20 ± 1.32 y; weight: 76.80 ± 15.40 kg; height: 1.73 ± 0.56 m; RT experience: 1.80 ± 1.23 y) via systematic counter-balancing order based on pre-experiment Z-score of one-repetition maximum (1 RM) bench press (BP) and handgrip strength ranking. The FG group used Fat Gripz™ attachments throughout the 8-week experimental period, utilizing six upper-body exercises (chest BP, inclined BP, chest flies, pull-ups, bent-over rows, and cable lateral raises). In contrast, the NFG group performed the same exercises without grips. A progressive overload training program was prescribed for both groups with intensity increasing from 60–80% of one-repetition maximum (1-RM) between weeks 1–8. No significant differences between FG and NFG groups were observed for both the 1-RM bench press and the handgrip strength tests in the pre- and post-test. However, within the FG group, significant improvement was observed in the 1-RM bench press (p = 0.001) and handgrip strength tests for both the non-dominant (p = 0.004) and dominant (p = 0.007) hands compared to their pre-intervention values. In contrast, the control group showed significant improvement only in the 1-RM bench press test (p = 0.001) with no significant changes seen in handgrip strength. In conclusion, this study found thick-bar resistance training capable of inducing significant improvement in handgrip strength for the experimental group.