The authors investigated whether baseline and therapy process characteristics of 82 heterosexual men participating in an Internet-based sex therapy study predict posttreatment sexual functioning. Problem severity, baseline sexual desire and baseline sexual satisfaction, but also partner problems and quality of the therapeutic relationship are predictive for sexual functioning and sexual satisfaction after finishing Internet-based sex therapy. The obtained outcome predictors could benefit men with sexual dysfunctions by tailoring online therapy programs to their individual characteristics. In addition, therapists should realize that clients suffering from erectile dysfunction or premature ejaculation in online sex therapy attach great importance to the therapeutic relationship.