Use of boron compounds has not become widespread because of the hardening and the other related problems in cementitious composites. The boron compounds as an additive material can be used widely in the production of cement and concrete in case of the elimination of these negative conditions. Thus the control of workability and hydration process of fresh concrete and mortar, some technological properties such as fire resistance, the radiation impermeability of hardened concrete and mortars can be enhanced. In this study, the effects of accelerating admixtures to the mechanical properties of boric acid added mortars were investigated. In order to determine of these effects and the results obtained to compare with those of control mortars, prismatic mortar samples were prepared in accordance with TS 196-1. Boric acid was added to mortar samples by up to 1% from 0.25% by weight of cement. Boric acid was not added to control mortar samples. Portland cement, boron modified active belite cement and calcium aluminate cement as binding material were used in mortar samples. 2, 7, 28 day compressive strengths and 28 day flexural strengths of 315 prismatic samples which were prepared in accordance with the design of 35 different mixes were determined. Results of boric acid added mortar samples were compared with control samples produced by using Portland cement, BAB cement and CAC cement. 2, 7, and 28 day compressive/flexural strength of mortar samples which were added 1% boric acid was determined as 0/0, 12.8/2.90, 40/6 MPa, respectively. Other hand, 2, 7, and 28 day compressive/flexural strength of mortar samples which were added 1% boric acid and 2% sodium aluminate was determined as 14.2/3.07, 27.2/5.57, 34.2/5.97 MPa, respectively. As a result, the retarding effect of the boric acid in terms of early strength of concrete was suppressed using sodium aluminate.