INTRODUCTION: Different techniques can be utilized in vitro to evaluate the durability of the bond strength to tooth structure. Shear bond strength test is one of these methods which have been widely used. Glass carbomer has been introduced with claims of improved physical characteristics in comparison with conventional GICs. OBJECTIVES: The aim of the study was to compare and evaluate the shear bond strength of glass carbomer to primary dentin versus a high viscosity glass ionomer (Fuji IX GP) MATERIAL AND METHODS: Twenty primary molar teeth extracted for orthodontic purposes or exfoliated by normal shedding were collected according to specific criteria from public hospitals in Alexandria and outpatient clinic of the Faculty of Dentistry, Alexandria University. Crown surfaces of the included teeth were mounted in acrylic blocks then, ground with water-cooled silicon carbide abrasive papers successively to obtain flat dentin surfaces. The prepared specimens (n=20) were divided into two groups according to the glass ionomer cement (GIC) bonded to the dentin surface (10/ each group): group I (Fuji IX GP) and group II (Glass Carbomer). Shear bond strength (SBS) between dentin surface and the bonded material was measured using a universal testing machine. RESULTS: The results revealed that, Fuji IXGP group recorded the highest mean SBS value (6.624) while, Glass Carbomer recorded mean value (2.870). There was a highly significant difference in shear bond strength values between both groups (p= 0.000). CONCLUSIONS: The high viscosity glass ionomer was higher in shear bond strength than glass carbomer glass ionomer and this finding may be salutary in GICs selection by dental practitioners.