Retinal ganglion cells (RGC) are the first neurons generating action potentials in the visual pathway. In order to convert presynaptic inputs from bipolar and amacrine cells into meaningful output, spike generation in RGCs must be robust in different scenarios. While spike generation is mostly influenced by biophysical properties of RGCs, here we investigated the influence of dendritic morphology on action potential dynamics, thresholds and firing rates in three types of mouse alpha RGCs.Tracings of ON-alpha sustained (ON-αs), OFF-alpha sustained (OFF-αs) and OFF-alpha transient (OFF-αt) RGCs in the wild-type mouse retina were reused from previous studies. Dendritic diameters were modified by the TREES toolbox in MATLAB. Multicompartment models of RGCs were developed in NEURON and the effect of dendritic morphology during intracellular and extracellular electric stimulation was compared. Using 3d-traced dendritic diameters we obtained cell-type specific parameters to reconstruct accurate RGC models in cases when no diameters were originally traced. Thresholds, i.e., the minimum current amplitude needed to elicit an action potential, were linearly dependent on dendritic diameters for intracellular stimulation and quadratically dependent for extracellular stimulation. Early action potential shape was strongly affected by proximal dendrite diameters.While our models suggest that biophysical properties such as sodium channel kinetics, density and distribution are mainly influencing spike generation in RGCs, our findings also indicate dendritic morphology to be a factor shaping neuronal responses such as action potential shape and thresholds. The developed fitting pipeline allows to extract cell-type specific parameters for the three mouse αRGCs.