This study assessed the effectiveness of neem (Azadirachta indica) leaf extract in controlling fall army worm (Spodoptera frugiperda) infestations in smallholder maize gardens in Ikulwe Village, Mayuge District, Uganda. The fall army worm (FAW), an invasive pest that first entered sub-Saharan Africa in 2016, had rapidly established itself as the most economically destructive pest of maize in Uganda, causing yield losses estimated at between 20% and 73% depending on infestation severity and management response. The study employed a randomised complete block design (RCBD) with four treatments: neem leaf extract at 100g/L, neem leaf extract at 200g/L, a positive control (lambda-cyhalothrin 5EC), and a negative control (distilled water). Data were collected on larval mortality rate, leaf damage score, and grain yield across three blocks over two growing seasons. Results indicated that neem leaf extract at 200g/L achieved a mean larval mortality rate of 72.4% and a leaf damage score of 2.1 (out of 9), comparable to the chemical control treatment (76.8% mortality, damage score 1.9) and significantly superior to the negative control (18.3% mortality, damage score 6.8). Grain yields in plots treated with 200g/L neem extract (3.12 t/ha) were notsignificantly different from those in chemical control plots (3.28 t/ha). The study concluded that neem leaf extract at 200g/L constituted an effective, affordable, and environmentally sustainable alternative to synthetic insecticides for FAW management among smallholder maize farmers.