Label acquisition projects with the grey parrot (Psittacus erithacus) demonstrated cognitive and communicative skills of this species comparable to great apes. However, results differ profoundly between individuals and laboratories. Two studies investigated the relationship between the characteristics, behaviors and attitudes of human trainers and caregivers, and the word-like sound production of grey parrots. In Study 1, 78 student subjects, who had trained two parrots for five years in our laboratory with the model/rival technique (used to teach animals to use vocal labels in a symbolic way), filled out the personality questionnaire NEO-Five Factor Inventory (Costa & McCrae, 1992) and answered additional questions about motivation, approach to animals, etc. Parrots’ communication during sessions with individual trainers was associated with higher agreeableness, a more serious approach to training, and a shorter period of time serving as a trainer. In Study 2, 29 pet owners and their respective parrots were tested using analogous questions used in Study 1. Results confirmed the effect of agreeableness and a serious approach to training on the production of human words uttered by parrots. In addition, pet owners with higher interest in bird communication had parrots that produced more words. Both studies indicate that the success of communication projects with grey parrots or other species might have been influenced by the characteristics of trainers/caregivers and their relationships with the trained animals.