The synergistic application of biochar and nitrogen fertilizer significantly improves plant growth and soil properties. The present study aimed to evaluate the effect of the application of biochar and nitrogen on the shoot and root of lemongrass in a factorial design within a completely randomized setup. The experiment included three levels of biochar, i.e. 0%, 1%, and 2% (v/v) and 2 levels of nitrogen, i.e. 0 and 1 (g/pot) under greenhouse conditions with 3 replications. The following parameters were measured, plant height, number of tillers, number of leaves, length of the largest leaf, fresh, shoot and root dry weight. The results indicated that biochar had a significant effect only on root growth and the number of tillers, while nitrogen fertilizer had a significant effect only on some shoot parameters. Root fresh weight, root dry weight, and root volume were significantly higher in the biochar-treated groups compared to the non-biochar-treated samples. Specifically, the root dry weight in the 2% biochar-treated group was 70% higher than in the non-treated plants. Additionally, the highest correlation between root and shoot characteristics of lemongrass was found between root parameters and the number of tillers per plant (r = 0.72). The number of tillers per plant was 60% higher in the biochar-treated group (2%) compared to the control group, and the number of tillers per plant correlated with the shoot dry weight (r = 0.56). Although the interaction between biochar and nitrogen fertilizer was not significant, their combined application enhanced root and shoot growth in lemongrass plants, thereby improving overall crop performance.