Research has shown that attitudes of students towards peers with disabilities are neutral, which shows the urge of promoting more positive attitudes among students. This longitudinal study was set up to analyze the effect of 1) knowledge about disabilities, and 2) the experience with a peer with disabilities on kindergarten students’ attitudes. The sample comprised two experimental classes and one control class (Nexp.1= 22, Nexp.2= 18, Ncontrol= 31) (age range 4-6). Attitudes were measured four times in a two year period. The classes can be described as follows: Experimental class 1 contained, 1) a knowledge intervention program, and 2) experience with peers with disabilities within the school. The knowledge intervention program was implemented between measurement time 1 and 2 and the experience with peers with disabilities at measurement time 4. Experimental class 2 contained only experience with a child with a disability within the class which started at measurement time 1. Control class did not contain knowledge and experience. The Acceptance Scale for Kindergarten - revised was used to assess attitudes at the four measurement times. The outcomes of the multilevel analysis showed both knowledge about disabilities and contact with peers with disabilities positively influence attitudes of kindergarten students.