The modification of jet shapes in Pb-Pb collisions, relative to those in $pp$ collisions, is studied for jets associated with an isolated photon. The data were collected with the CMS detector at the LHC at a nucleon-nucleon center-of-mass energy of 5.02 TeV. Jet shapes are constructed from charged particles with track transverse momenta (${p}_{T}$) above $1\text{ }\text{ }\mathrm{GeV}/c$ in annuli around the axes of jets with ${p}_{T}^{\text{jet}}>30\text{ }\text{ }\mathrm{GeV}/c$ associated with an isolated photon with ${p}_{T}^{\ensuremath{\gamma}}>60\text{ }\text{ }\mathrm{GeV}/c$. The jet shape distributions are consistent between peripheral Pb-Pb and $pp$ collisions, but are modified for more central Pb-Pb collisions. In these central Pb-Pb events, a larger fraction of the jet momentum is observed at larger distances from the jet axis compared to $pp$, reflecting the interaction between the partonic medium created in heavy ion collisions and the traversing partons.