Area codes in Oshawa, Ontario
Oshawa, Ontario uses 4 area codes — 905, 289, 365 and 742. The main Oshawa area code is 905.
Area codes serving Oshawa
Phone numbers in Oshawa are written as ten digits — for example (905) 555-0190 — and fall in the Eastern Time zone.
How Oshawa came to have 4 area codes
The original Oshawa area code is 905, in service since 1993. As the area ran low on available numbers, overlay codes were added over the same region for new phone lines: 289 (2001), 365 (2013) and 742 (2021). Existing numbers kept their original code — an overlay never forces anyone to change their number — which is why Oshawa now uses all 4 codes and every local call is dialed with ten digits.
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More cities in Ontario
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Frequently asked questions
What is the area code for Oshawa?
The main area code for Oshawa, Ontario is 905. Oshawa is now served by 4 area codes in total: 905, 289, 365, 742.
How many area codes does Oshawa have?
Oshawa has 4 area codes: 905, 289, 365, 742.
Why does Oshawa have more than one area code?
As Oshawa used up the numbers available in its original area code (905, in service since 1993), additional "overlay" codes were added over the same area so new phone numbers could keep being assigned.
How do you dial a Oshawa number?
Dial all 10 digits — the area code (905 or 289 or 365 or 742) followed by the 7-digit local number. From abroad, dial +1, then the area code and number.
Sourced from the official NANPA (North American Numbering Plan Administrator) numbering database, current as of August 2, 2026. Refreshed monthly.