In this paper we discuss some of the factors sport psychologists should consider before administering questionnaires or other formal assessment instruments to athletes. To be used effectively, assessment instruments need to be (a) reliable and valid for the individual athlete or sport group in question, (b) seen as useful by the athlete(s) completing the instrument, and be (c) completed honestly by the athlete(s). Additional objectives sport psychologists should strive to achieve include a clear identification of the purpose of the assessment instrument, the commitment of athlete and coach to the assessment process, and the maintenance of a clear channel of communication with coaches and athletes throughout the period of psychological assessment, training, feedback, evaluation, and adjustment.