Genotype, environment and agronomic practices are key determinants of crop   growth and productivity which are important to provide food, feed, raw materials and income to small holder farmers in Africa. The study was conducted at Crop museum, Sokoine University of Agriculture, Morogoro, Tanzania to investigate physiological response of groundnut to calcium and phosphorus nutrition among three improved groundnut genotypes Mangaka (G1), Masasi (G2) and Pendo (G3) with three levels of phosphorus and at calcium control (T0), 125 kg/ha (T1) and 55 kg/ha (T2) supplied from Diammonium Phosphate (DAP) and Minjingu mazao, respectively.  Significant (P< 0.05) influence of calcium was observed on leaf area index (LAI) 4.03; crop biomass 88.79 g/plant; number of nodules 66.22, and crop growth rate (CGR) 15.05 g m2/day. Whereas phosphorus had significant influence on net assimilation rate (NAR) 10.84 g m2/day. Similarly, groundnut genotype (Masasi) had significant influence on LAI (3.95); CGR (13.04 g m2/day); NAR (12.36 g m2/day) and number of nodes (64.93). However, there was no significant effect of genotype on crop biomass recorded from the investigation. Growth  parameters were significant influenced by genotype and fertilizer interactions with Significant (P=0.2) interaction effect for crop biomass observed between G3 x T1, whileG3 x T2 significantly affected number of nodules and G2 x T1 had Significant interaction effects on CGR and NAR. This is an indication that investment in improved genotype and appropriate application rate of fertilizers has the potential to enhance yield and income of smallholder farmers.