We present surface photometry and stellar kinematics of NGC 4431, a barred dwarf galaxy in the Virgo Cluster undergoing a tidal interaction with one of its neighbors, NGC 4436. We measured its bar pattern speed using the Tremaine-Weinberg method and derived the ratio of the corotation radius, DL, to the bar semimajor axis, aB. We found DL/aB=0.6+1.2-0.4 at 99% confidence level. Albeit with large uncertainty, the probability that the bar ends close to its corotation radius (i.e., 1.0<=DL/aB<=1.4) is about twice as likely as that the bar is much shorter than the corotation radius (i.e., DL/aB>1.4). Based on observations collected at the European Southern Observatory, Chile [ESO programs 71.B-0138(A) and 73.B-0091(A)].