The influence of plant spacing and intercropping on the growth and septoria leaf spot disease incidence and severity of tomato were studied in Owerri, the south east of Nigeria, in the year 2011.The study was designed as a 4x4 factorial in a Randomized Complete Block Design with three (3) replications. Data on growth parameters and septoria leaf spot disease incidence and severity of tomato were collected and statistically analyzed by using Gensat version 4 analytical software, while the means were separated for difference using Fisher’s Least Significant Difference Protocol. The result showed a significant (P<0.05) reduction of septoria leaf spot disease incidence to 0.00% by intercropping at the distance of 75 x 50 cm under tomato sole cropping arrangement. The intercrop combination of tomato/groundnut/soybean also significantly (P<0.05) reduced septoria leaf spot disease incidence (6.7%) under the spacing of 100 x 75 cm. Intercropping significantly (P<0.05) influenced septoria leaf spot disease severity at 6 weeks of transplanting. Similarly, plant spacing of 75 x 50 cm and under the tomato sole crop arrangement significantly reduced the tomato septoria leaf spot disease severity.