In Japan, small tomatoes have high quality. Soluble solids content is a critical factor for palatability. A non-destructive method for determining the soluble solids content in larger tomatoes using near-infrared (NIR) spectroscopy has been developed. However, a new spectral measurement method was needed to measure different-sized tomatoes including very small fruits (less than about 10 g) using an instrument. The introduction of interactance-transimission mode may improve the efficiency of collecting light from the small tomatoes. Therefore, the objective of this study is to develop a new spectral measurement method for small tomatoes using NIR spectroscopy. Multiple linear regression (MLR) analysis of spectra (800-1000 nm) of tomatoes (numbers of samples (n) = 60) gave a calibration equation using 2nd derivative values of absorbance at 856, 876, 900, and 952 nm with a multiple correlation coefficient of 0.97. The MLR calibration was validated using other small tomato sample lots. Nevertheless, they were predicted well with a root mean square of 0.41 (n = 36).