In this research, the seismic behavior of single-layer diamatic dome (SLDD) structures was analyzed under earthquake loads, and then the seismic response modification factors (SRMFs) of these structures were extracted. For this purpose, 16 models with different span lengths (SLs) and rise-to-span ratios (RSRs) were designed, and the effects of SL and RSR on the SRMFs of these structures were evaluated. Also, the effect of member density on the SRMFs was studied. The models were first designed under the applied loads based on relevant design codes. Then, by performing the nonlinear time history analyses using the three translational components of ground motion records, the control point and target displacement in the horizontal and vertical directions were obtained to implement the pushover analyses. Thereafter, the pushover analyses were implemented by using the target displacements derived from the nonlinear time history analyses, and the SRMFs of SLDD structures in both horizontal and vertical directions were obtained. The results indicate that models with RSRs of 1/7 to 1/3 remained in the elastic range in the horizontal direction. For the models with an RSR greater than 1/3, if the RSR increases, the ductility and behavior factor increases in the horizontal direction. However, there is a downward trend in the vertical direction due to the increase in the vertical stiffness. The horizontal and vertical behavior factor was obtained in the range of 1.155–2.459 and 1.155–2.893, respectively. Finally, by using the results obtained and through the nonlinear regression analysis, equations were proposed for the period, target displacement, displacement amplification factor, and behavior factor for SLDD structures in terms of the SL and RSR in the horizontal and vertical directions. •The seismic response modification factors (SRMFs) of single-layer diamatic dome structures are extracted.•The effect of member density on the SRMFs is studied.•Equations were proposed for the period, target displacement, behavior factor, and displacement amplification factor.•The SRMFs of these structures are obtained in both horizontal and vertical directions.