Preheat oven to 350 degrees.
Add flour, cocoa, baking soda, and salt to a medium bowl. Stir together.
Beat butter and sugar in a large bowl with mixer until fluffy. Add eggs and vanilla; beat well.
Gradually add flour mixture, beating well. Stir in peanut butter chips.
Drop by rounded teaspoons onto ungreased cookie sheet. Bake 8-9 minutes (cookies will be soft, do not overbake).
Cool slightly on cookie sheet, remove and add to wire rack. Cool completely.