© 2014 American Physical Society.We study the effects of lepton flavor violation (LFV) in the scalar lepton sector of the MSSM on precision observables such as the W-boson mass and the effective weak leptonic mixing angle, and on the Higgs-boson mass predictions. The slepton mass matrices are parametrized in a model-independent way by a complete set of dimensionless parameters which we constrain through LFV decay processes and the precision observables. We find regions where both conditions are similarly constraining. The necessary prerequisites for the calculation have been added to FeynArts and FormCalc and are thus publicly available for further studies. The obtained results are available in FeynHiggs.