Denver general manager Tim Connelly announced the news Monday.
Arthur averaged nearly six points a game for Denver last season and knocked down a career-high 24 3-pointers. The Nuggets picked him up in a draft-night trade last June.
Robinson scored 10.4 points and dished out 2.5 assists last year for the Nuggets before a knee injury on Jan. 29 ended his season. In his career, the diminutive point guard has also played for Chicago, Golden State, Oklahoma City, Boston and New York.