The main goal of this study is to investigate inheritance of some economic characters of squash genotypes and its hybrids and reciprocals. This experiment was carried out during 2017 and 2018 seasons. Ten advanced inbred lines of summer squash (Cucurbita  pepo L.) named MHSQ-1= P1, MHSQ-2= P2, MHSQ-3= P3, MHSQ-4= P4, MHSQ-5= P5, MHSQ-6= P6, MHSQ-7= P7, MHSQ-8= P8, MHSQ-9= P9 and MHSQ-10= P10 were planted in Misr Hytech seed int. Co. research farm. The advanced 10 inbred lines were used in complete diallel mating design to study genetic parameters of some economic characters viz., number of days to first female flower (D.F.F.F.), sex ratio, fruit weight (F.W. g), total soluble solids percentage (T.S.S %), number of fruits per plant (N.F.P.) and total yield per plant (T.Y.P. g)  of resulted ninety straight and reciprocal F1 hybrids relative to mid and better parents and two commercial check cultivars ''Aziad and New Eskandarani''. Results of mean squares for (D.F.F.F.) traits exhibited that significant or high significant for all types of variations. Moreover, sex ratio was high significant for all types of variations. Mean squares for fruit weight (F.W.) was significant or high significant for all types of variations except reciprocal effect. T.S.S recorded insignificant values of mean squares. Mean squares for (N.F.P.) and (T.Y.P.) characters were found high significant. Heterosis for (D.F.F.F.) and sex ratio traits showed different levels of significance with positive and negative values except some hybrids. Heterosis  (F.W ) and (T.S.S.) exhibited some hybrids with significant or high significant positive or negative values.     Heterosis for (N.F.P.) and (T.Y.P.) showed several hybrids having different heterotic effects. Phenotypic Correlation coefficient analysis showed different degrees of correlations between all studied traits.