<p>Light intensity and substrate moisture content are critical environmental factors influencing the productivity of greenhouse cherry tomatoes (<i>Lycopersicon esculentum</i> var. cerasiforme A. Gray). This study investigated their combined effects on cherry tomato growth, yield, and quality. Experiments were conducted in the springs of 2022 and 2023, utilizing two light intensity levels (natural light, L1; 70% natural light, L2) and four substrate moisture content levels (W1: 35%–45%, W2: 45%–55%, W3: 55%–65%, W4: 65%–75%). Comprehensive growth performance was evaluated using the Analytic Hierarchy Process (AHP) and Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) methods, and a quadratic regression model was established to analyze trends. Results indicated that both light intensity and substrate moisture content significantly affected the comprehensive growth of cherry tomatoes. Under natural light conditions (L1), stem diameter, net photosynthetic rate, dry matter accumulation, and yield all increased with substrate moisture content, peaking at the W3 level. Under low-light conditions (L2), the W1 level was identified by the TOPSIS model as most beneficial for overall growth performance, although the W3 level produced the highest yield and dry matter accumulation. The quadratic regression model further revealed that, under consistent light conditions, the overall performance score of cherry tomatoes initially increased with substrate moisture content, reached a peak, and then declined. Based on these findings, we recommend maintaining the optimal substrate moisture content for greenhouse cherry tomatoes at W3 (55%–65%) under natural light conditions, and at W1 (35%–45%) under low-light (70% natural light) conditions. This study provides a robust theoretical foundation for developing targeted irrigation strategies tailored to varying light intensities in greenhouse cherry tomato cultivation.</p>