Improving water use efficiency is an effective way to conserve water in agriculture. Drip irrigation is a water-saving irrigation technology that has been adopted worldwide. Film mulching can prevent undesired water vaporization losses and enhance soil surface temperature. This study used a meta-analysis to assess the effects of mulching on crop yield (CY) and water use efficiency (WUE) under drip irrigation to determine whether a superposition effect occurs when combining film mulching and drip irrigation and whether the limiting factors of film mulching play a positive role in agricultural production. The results showed that film-mulching drip irrigation (FMDI) increased CY and WUE by about 20% and 30%, respectively, compared with nonmulching drip irrigation (NMDI). These improvements were affected by climatic conditions (climate), soil conditions (SC), crop type (CT), water consumption (WC), and mulching material (MM). For climate, film mulching was most effective in areas with temperature (Te) values below 10 °C and rainfall (RF) less than 400 mm, increasing CY by 17.6% and WUE by 16.2%. For SC, FMDI improved CY and WUE the most in medium-textured (loam) soil types with less than 17% plant available water capacity. As water consumption increased, the effect size of CY and WUE under FMDI decreased. For CT, FMDI increased vegetable CY (13.3–17.5%) and field crop WUE (12.3–53.7%). MM had no significant effect on improving CY or WUE. This study provides a reference for the practice of film mulching under drip irrigation conditions.