There is scarce scientific information regarding the potential benefits of healthy lifestyles in patients with hidradenitis suppurativa (HS). The objective of this study is to explore the potential association between the adherence to a Mediterranean diet (MD), physical activity and HS severity. A cross-sectional study that included patients with HS was conducted. Disease severity was evaluated by the International Hidradenitis Suppurativa Severity Score System (IHS4) and self-reported disease activity using a Numeric Rating Scale (NRS, 0−10). The adherence to a MD was assessed by the PREvención con DIeta MEDiterránea (PREDIMED) questionnaire and the level of physical activity by the International Physical Activity questionnaire. A total of 221 patients with HS were included in our study. The adherence to a MD was average for a Spanish population. A higher adherence to a MD was associated with lower disease activity, lower self-reported Hurley and lower IHS4. The use of extra virgin olive oil as the main culinary lipid was the dietary habit that implied a lower degree of disease activity (p < 0.05). Regarding physical activity, both the self-reported severity and IHS4 presented an inverse association with the intensity of physical activity. The adherence to a MD and the intensity of physical activity were positively associated. The Mediterranean dietary pattern may have an impact on HS. Greater adherence to a MD is related to lower HS severity and more physical activity also correlates to lower disease severity. The MD could be an appropriate dietary pattern for patients with HS due to its anti-inflammatory properties, and combining this with increased levels of physical activity could have additional benefits.