We have imaged the field of GRB 100305A (Troja et al., GCN 10470) with the automated Palomar 60-inch telescope. Images were obtained in the Sloan g', r', i', and z' filters beginning at 09:09 UT on 5 MarcHETE 2010 (~ 3.5 minutes after the burst). In coadded images, we find no sources inside the XRT error circle to the following limits (calculated with respect several point sources in the SDSS DR7 catalog): Filter Mid-point t_burst Exposure Magnitude ------------------------------------------------------------------------- r' 09:25 19.5 min 720.0 > 22.0 z' 09:27 21.7 min 420.0 > 20.5 i' 09:28 23.3 min 660.0 > 22.0 The lack of an optical afterglow candidate, together with the long duration and lack of X-ray absorption in excess of the Galactic value (Troja et al., GCN 10470), make GRB 100305A a candidate high redshift event. We encourage additional follow-up at longer wavelengths.