Objective: This study was performed to evaluate bond strength of a new self-etch self-adhesive / flowable composite in comparison with one step-self etch adhesive / flowable composite and two step total-etch adhesive / flowable composite.Materials and methods:Shear bond strength of the investigated material to middle dentin of primary teeth was evaluated after 24 hours. A total of thirty caries free , freshly extracted primary molar were utilized in this study. Teeth were divided into three groups according the material used (n = 10 per group).Buccal surface of acrylic embedded molars were ground into flat dentin surface ,to which material were applied according to manufacture instruction composite was applied split Teflon plate to form cylinders (2mmin diameter and 2mm in height)were constructed on the buccal surface of specimens to which shear-force was applied to a failure using A universal testing machine at a crosshead speed, 0.5mm/minute. After the test procedure, fractured surfaces were observed using a stereomicroscope (50X) to determine the failure mode. Representative sample per each group were investigated resin /dentin interface under scanning electron microscope.Results: It was found that Total etch group recorded statistically non-significant highest shear bond strength mean value (11.98 ± 2.463 MPa) followed by Self etch group (11.23 ± 1.196 MPa) while Vertise group showed the lowest statistically non-significant shear bond strength mean value (10.65 ± 1.497 MPa) as indicated by ANOVA test followed by Newman Keuls post-hoc test (P>0.05). Evaluation of the failure modes after shear testing indicated that high bond strength showed predominently cohesive or mixed modes, while low bond strength groups to exhibit predominently adhesive modesResin –dentin interface treated with total etch adhesive demonstrated a large number of resin tags ,while fewer number of resin tags was observed with self etch adhesive system .However very few resin tags was observed when self etch self adhesive flowable composite was used.Conclusion: The shear bond strength of the total-etch adhesive, self-etch adhesive / flowable composite and self-etch self-adhesive flowable composite to primary tooth dentin was nearly similar with no significant difference. Total etch adhesive revealed the highest score of cohesive failure mode whereas the self-adhesive flowable composite revealed the highest score adhesive failure mode. There may be no clear correlation between the dentin in bond strength and mode of failure. The acidity of the adhesive material may be correlated to its penetration ability to primary tooth dentin.