This paper presents a numerical study of blade fouling effects on compressor performance and tonal noise emission. First of all, the numerical approach is validated against measurements, and it is shown that predictions agree fairly well with experimental data. Then, various cases with different conditions of fouling are investigated where fouling is modeled by increasing blade surface roughness. In addition, uniform blade fouling is considered in all cases. Results from these cases show that the total-to-total pressure ratio and isentropic efficiency gradually decrease as the blade fouling becomes more severe, which is mainly caused by reversed flows at the blade leading edge. Moreover, it is found that while blade fouling trivially affects compressor tonal noise in moderate fouling cases, it does increase broadband noise. Overall, this paper gives insight into blade fouling effects on both compressor performance and acoustics.