Introduction: This study examined the effects of group art therapy on depression, burden, and self-efficacy in primary family caregivers of patients with brain injuries. Method: This was a quasi-experimental, nonequivalent control group and a pre- and post-test design. This study was carried out in one national rehabilitation hospital targeting 41 primary family caregivers of patients with brain injuries. Group art therapy intervention was carried out three days per week comprising 12 sessions over four consecutive weeks. The experimental group (n = 20) received group art therapy, whereas the control group (n = 21) did not. We used a time difference method to minimize the risk of contaminating the control group by sampling sequentially. Results: For depression, although there was a significant difference after the intervention (t = 3.296, p = 0.004), the mean difference score was not statistically significant between the experimental group and the control group (t = 0.861, p = 0.395). The experimental group showed a significantly greater decrease in burden (t = 2.462, p = 0.020) and significantly greater improvement in self-efficacy (t = −6.270, p < 0.001) than the control group. Conclusions: Group art therapy may be an effective nursing intervention for primary family caregivers of patients with brain injuries.