We investigated the influence of post-traumatic growth (PTG) and mental health (MH) on multiple sclerosis (MS) caregivers’ uses of coping strategies and identified biopsychosocial predictors of proactive or reactive coping. The Short Form Health Survey (SF-12), General Health Questionnaire (GHQ-28), Post-Traumatic Growth Inventory (PGI-21), Brief COPE Questionnaire (COPE-28), and Multidimensional Scale of Perceived Social Support (MSPSS) were used to evaluate 209 caregivers. Higher PTG was related to greater use of emotional support, positive reframing, religion, active coping, instrumental support, planning, denial, self-distraction, self-blaming, and venting. Better MH was associated with greater use of acceptance, while behavioral disengagement and self-distraction were associated with poorer MH. The PTG dimensions relating to others and new possibilities, SF-12 dimensions of physical and emotional roles as well as partnership, not living with the patient, and significant others’ social support were predictors of proactive coping. Reactive coping was positively predicted by the PTG dimension relating to others, depression, vitality, other than partner relation, and physical role, and negatively predicted by mental health level and emotional role. In summary, higher MH was associated with proactive coping strategies, whereas post-traumatic growth was related to the use of a wide range of proactive coping as well as reactive coping strategies.