We investigate the effects of gravitational lensing due to intervening galaxies on the recently discovered Type Ia supernova at z~1.7, SN 1997ff, in the Hubble Deep Field North. We find that it is possible to obtain a wide range of magnifications by varying the mass and/or the velocity dispersion normalization of the lensing galaxies. In order to be able to use SN 1997ff to constrain the redshift-distance relation, very detailed modeling of the galaxies to control the systematic effects from lensing is necessary. Thus, we argue that, based on our current limited knowledge of the lensing galaxies, it is difficult to use SN 1997ff to constrain the values of {Omega}_M_ and {Omega}_{Lambda}, or even to place severe limits on gray dust obscuration or luminosity evolution of Type Ia supernovae.