Silicon actuation can influence the physiological parameters and nitrogen metabolism of pepper. The aim of this study was to (i) investigate the silicon action on nitrogen metabolism and (ii) elucidate the mechanism responsible for osmotic adjustment in two Capsicum annuum cultivars with high commercial values exposed to water deficiency. Experimental design used was a completely randomised factorial layout composed of five water and Si treatment combinations (control, deficit + 0.00, deficit + 0.25, deficit + 1.00, and deficit + 1.75 μM Si), applied to two cultivars (Ikeda and Vermelho Gigante) with six replicates. Parameters evaluated were leaf relative water content, stomatal conductance, transpiration rate, nitrate reductase activity, free ammonium, total soluble amino acids, total soluble proteins, proline and glycinebetaine. Proline levels in both cultivars were increased with silicon application in 0.25 µM Si, if compared with the control and deficit + 0 µM Si. A higher glycinebetaine concentration was found in Ikeda cv. at 0.25 µM Si, when compared to control and deficit + 0 µM Si. The data suggests positive inference of silicon on water relations and nitrogen compounds, and an improvement in osmotic adjustment in Capsicum annuum plants exposed to water deficit. Proline and glycinebetaine contribute to osmotic adjustment in Ikeda, while this process in Vermelho Gigante is carried only by glycinebetaine.