Magnetic properties R(Fe1−xCox)11.3Nb0.7 compounds have been investigated. All of the compounds crystallize in the tetragonal ThMn12 structure. The unit cell volume slightly decreases with increasing Co content for both systems. Curie temperature (TC) almost increases linearly with increasing Co content for both systems. The maximum of saturation magnetization (Ms) appears around x=0.2 in Ho(Fe1−xCox)11.3Nb0.7 and x=0.15 in Y(Fe1−xCox)11.3Nb0.7 compounds at 5 K. The easy magnetization directions of all compounds are along the crystallographic c axis at room temperature. Thermomagnetic analysis shows that there exists no spin reorientation in the whole ordering temperature range. The magnetocrystalline anisotropy field Ba of Y(Fe1−xCox)11.3Nb0.7 exhibits a maximum with x=0.10 at 5 K and x=0.05 at room temperature, while Ba of Ho(Fe1−xCox)11.3Nb0.7 decreases monotonically with the increasing Co content at room temperature. First-order magnetization process (FOMP) has been observed in Ho(Fe1−xCox)11.3 compounds at low temperature.