Criminal Investigations   This unit consists of the following seven sub-units:

Fraud Unit This Unit is made up of three Constables who investigate fraudulent transactions such as significant financial losses to individual and businesses, mail and Internet fraud, cheque and credit card fraud, and identity theft. Many of the investigations are complex, multi-jurisdictional or transnational investigations. Members of the Unit also provide training to the banking community and offer information sessions to community groups such as seniors. The unit also regularly issues media alerts on current fraud scams. Persons Crime Unit This Unit is made up of a Sergeant and three Constables. The unit investigates crimes such as homicides, suspicious deaths, missing persons, serious assaults, robberies, hate crimes, and other crimes against persons.

Property Crime Unit
This Unit is made up of a Sergeant and three Constables. They investigate offences such as commercial and residential break and enters, suspicious fires, and stolen property. They also assist in the investigation of other significant crimes.

Sexual Assault and Child Abuse Unit
This Unit is made up of a Sergeant and four Constables. The unit investigates sexual assault and child abuse complaints. They are also responsible for maintaining and tracking offenders who are required to register with the Ontario and National Sex Offender Registry. These registries are available to the police for law enforcement investigative purposes.

Technical Crimes
In 2007 the Guelph Police Service formed a Technical Crimes Unit. The one officer in the unit specializes in retrieval of data from computers, cellular telephones and other digital equipment. The officer is responsible for investigating Internet child exploitation and joined other Ontario police services in a Provincial initiative to combat child on-line exploitation. This co-ordinated effort will involve the sharing of resources and expertise between police services, while maintaining a community based approach to a global problem.

The member also conducts community presentations to educate the public on Internet safety.

Youth Office
The two Constables in the Youth Office investigate offences involving crimes committed by youth under the age of 18. The officers also track all police contact with young persons under the Youth Criminal Justice Act. Members also work together with various community agencies and schools as the police respond to youth issues throughout the city.

Identification
The Identification unit consists of four Constables who are responsible for the collection and processing of physical exhibits and for all photography that might be utilized in a judicial hearing or a coroner's inquest.

Technologies currently in use include electronic measuring devices and computerized plotting programs for scale diagrams, cyano-acrylate glue fuming chambers and alternate light sources to make latent fingerprints visible, digital image enhancement software, video analysis software, computer programs that permit the directional analysis of projected bloodstains (BackTrack) and digital mug shot retrieval programs that permit officers to quickly view hundreds of photos for their possible inclusion in a photo line-up.