Porous substrates have gained increased usage in cell studies and tissue mimetic applications because they can partition distinct cell types while still allowing important biochemical crosstalk. In the presented work, we investigated how porous substrates with micron and submicron features influence early cell migration and the associated ECM establishment, which can critically affect the rate of cell coverage on the substrate and the ensuing tissue organization. We showed through time-lapse microscopy that cell speed and migratory distance on membranes with 0.5 μm pores were nearly two-fold of those observed on nonporous membranes, while values on membranes with 3.0 μm pores fell in between. Although the cell directionality ratio and the persistence time was unaffected by the presence of pores, the cells did exhibit directionality preferences based on the hexagonal pore patterning. Fibronectin fibrillogenesis exhibited a distinct inverse relationship to cell speed, as the fibrils formed on the nonporous control were significantly longer than those on both types of porous substrates. We further confirmed on a per cell basis that there is a negative correlation between fibronectin fibril length and cell speed. The observed trade-off between early cell coverage and ECM establishment thus warrants consideration in the selection or the engineering of the ideal porous substrate for tissue mimetic applications and may help guide future cell studies.