In vivo imaging permits longitudinal study of ocular disease processes in the same animal over time. Two different in vivo optical imaging modalities – optical coherence tomography (OCT) and fluorescence – provide important structural and cellular data respectively about disease processes. In this Methods in Eye Research article, we describe and demonstrate the combination of these two modalities producing a truly simultaneous OCT and fluorescence imaging system for imaging of fluorescently labeled animal models. This system uses only a single light source to illuminate both modalities, and both share the same field of view. This allows simultaneous acquisition of OCT and fluorescence images, and the benefits of both techniques are realized without incurring increased costs in variability, light exposure, time, and post-processing effort as would occur when the modalities are used separately. We then utilized this system to demonstrate multi-modal imaging in a progression of samples exhibiting both fluorescence and OCT scattering beginning with resolution targets, ex vivo thy1-YFP labeled neurons in mouse eyes, and finally an in vivo longitudinal time course of GFP labeled myeloid cells in a mouse model of ocular allergy.