Viewers can now download episodes of the current series of CSI: Miami, a week before their UK transmission.
The site also gives online access to the most recent series of CSI: Crime Scene Investigation; CSI: NY and CSI: Miami, with plans to make the entire CSI back catalogue available.
The move marks the first time the internationally popular show has been offered on-demand outside of the US.
Five has partnered with BT Media & Broadcast to develop the service, as part of the five.tv website.
It is charging £2.49 for previously-unseen programmes and £1.49 for all other episodes.
Five to offer CSI on-demand
Five has launched its video-on-demand service, Five Download, beginning with episodes of its biggest show, Crime Scene Investigation.