Tomato though a day neutral crop, is predominantly cultivated during the cool dry harmattan partly due to low incidence of diseases and favourable low temperature. The scarcity of fresh tomato outside this season needs to be considered to meet the teeming demand of the populace. Knowledge of the nature of association between yield and its components is of great necessary in any breeding programme. It was against this background that a field experiment was conducted in 2008 and 2009 at Salam Farm of Ngaburari village of Konduga Local Government Area of Borno State (Lat. 12°N and Long. 13°13’E) in the Semi-Arid Region of Nigeria to determine the relationship between yield and other agronomic parameters as affected by mulching and cultivars of tomato (Lycopersicon lycopersicum L. Karst) during the heat period to provide effective tool for breeders. The treatments consisted of five cultivars of tomato (Tandino, Danbaga, Roma VF, UC82B and Dansyria) and six grass mulch (Pennisetum pedicelatum Trin) levels (0 t/ha, 2.5 t/ha, 5 t/ha, 7.5 t/ha, 10 t/ha and 12.5 t/ha) which were laid out in a strip-plot design and replicated three times. The parameters studied include plant height, number of leaves, leaf area, leaf area index, number of branches per plant, days to first and 50 % flowering, number of fruits, weight of fruits per plant and yield in t/ha. Data collected were subjected to Correlation Analysis using Statistic 8.0 and the results of the combined years for cultivars indicated that total fruits yield was significantly and positively correlated with plant height, number of leaves, leaf area, leaf area index, days to first flowering and weight of fruits but significantly negatively correlated with days to 50 % flowering. Similarly, correlation of parameters as affected by mulch indicated significant and positive correlation of fruit yield with plant height, number of leaves, leaf area, leaf area index days to first flowering, number of fruits and weight of fruits but significantly negatively correlated with number of branches and days to 50 % flowering. Days to first flowering had significant positive correlation with days to 50 % flowering, number of fruits and weight of fruits both as affected by cultivar and mulch. Hence selection for high yield during heat period in the semi arid region of Nigeria should be based on earliness to flowering.