Abstract: Ear Length (EL), Ear Diameter (ED), number of rows per ear (RE), kernel number per row (KR) and 100 Kernel Weight (KW) are the most important yield components (YCTs) of grain yield in maize (Zea mays L.). Many investigations have been conducted on grain yield combining ability and the results have been widely used in maize breeding programs. Limited research has been done on combining ability of maize YCTs, however, no reports on the relationship between grain yield combining ability and YCTs combining abilities exist. The objectives of this study were to estimate combining abilities of grain yield and of EL, ED, RE, KR and KW and examine the relationship between grain yield combining abilities and the combining abilities of the YCTs. Both general (GCA) specific (SCA) combining ability and reciprocal mean squares were highly significant for all studied traits excepted Ear Length (EL), Ear Diameter (ED), number of rows per ear (RE) and 100 kernel weight for (GCA) and Ear Diameter (ED) and number of rows per ear (RE) for (rij). The ratio of GCA/SCA was less than unity for all studied traits. These results indicating that the non-additive genetic effects were more important and played the major role in all studied traits indicating the non-additive gene was more important than additive gene action. The ratio of GCA/SCA for grain yield and for the YCTs were between 0.006 and 0.65, indicating non-additive genetic effects were more important for these traits. The results showed the general combining ability GCA effects for six parental line indicating that the parental inbred line P4 was good combiner for Ear Length (EL) and number of rows per ear (RE). The parental inbred line P5 was good combiner for kernel number per row (KR) and the parental inbred lines P1 was good combiner for grain yield (ard/fed). This study also showed that the GCA effects of grain yield were related to YCTs’ GCA effects in an inbred line and the SCA effects of grain yield were also related to the YCTs’ SCA effects in the same crosses. Significantly positive grain yield SCA effects usually were highly correlated with the number of the YCTs that had significantly positive SCA effect, i.e., all the F1 crosses out yielded significantly better than the check SC162, except four crosses. Single crosses (P4xP1) was significantly better than the best check SC155 for grain yield, however, there were seven single crosses, i.e., (P5xP4), (P4xP2), (P1xP4), (P1xP5), (P2xP3), (P6xP1) and (P2xP6) which statistically equal the check cross 155. For (SCA) effects of the 15 F1 crosses had positive and highly significant effects. However for maternal effect or reciprocal (SCA) effects were found that single crosses i.e, (P5xP4), (P3xP6), (P4xP2), (P5xP3), (P1xP3) and (P6xP1) yielded highly significant for grain yield. Thus, selecting inbred lines with positive GCA effects in either all or most of YCTs will have greater chance to obtain crosses with higher grain yield. The information of GCA and SCA effects for YCTs is very useful for maize breeders to determine which maize line should be selected to improve local lines and which parent lines should be used for making hybrids with greater grain yields.