NBC has officially canceled Constantine, according to Entertainment Weekly.  Production had been halted on the show after an initial 13-episode run which began airing last October.  There had been hopes the show would be extended to 26 episodes for its first season, but after production was shut down at NBC, the showrunner pleaded with fans to show their support for the show in the hopes that a late surge would convince the network to extend the order (see "'Constantine' Showrunner Asks for Support").

But it was not to be, and now Warner Bros. Television, which produces the show, may shop the series to other networks, according to the report.  The viewership, an average of 4.5 million viewers ages 18-49 over that first 13 episodes, weren’t enough for NBC but would look good a lot of other places, like say Time Warner network the CW, or NBC sister network Syfy, both of which have been rumored as targets.