A series of tetraarylchlorins with 3-methoxy-, 4-hydroxy- and 3-methoxy-4-hydroxyphenylmeso-aryl rings (1-3-Chl) and their Sn(IV) complexes (1-3-SnChl) were synthesized and characterized so that their potential utility as photosensitizer dyes for use in photodynamic therapy (PDT) and photodynamic antimicrobial chemotherapy (PACT) can be assessed. The photophysicochemical properties of the dyes were assessed prior to in vitro PDT activity studies against MCF-7 breast cancer cells through irradiation with Thorlabs 625 or 660 nm LED for 20 min (240 or 280 mW·cm−2). PACT activity studies were performed against both planktonic bacteria and biofilms of Gram-(+)S. aureusand Gram-(−)E. coliupon irradiation with Thorlabs 625 and 660 nm LEDs for 75 min. The heavy atom effect of the Sn(IV) ion results in relatively high singlet oxygen quantum yield values of 0.69−0.71 for1-3-SnChl. Relatively low IC50values between 1.1−4.1 and 3.8−9.4 µM were obtained for the1-3-SnChl series with the Thorlabs 660 and 625 nm LEDs, respectively, during the PDT activity studies.1-3-SnChl were also found to exhibit significant PACT activity against planktonicS. aureusandE. coliwith Log10reduction values of 7.65 and >3.0, respectively. The results demonstrate that the Sn(IV) complexes of tetraarylchlorins merit further in depth study as photosensitizers in biomedical applications.