Does addon domain affect SEO?

[Simi123]

Nope, this is just a feature with your web hosting companies control panel, it has no effect/effects on SEO. A addon domain is another domain name you attach to your webhosting account, allowing you to host 2 websites within the same hosting account. As long as you don't have the exact same website on both domains. You'll be fine, you shouldn't inter-link websites on the same host, as they'll all be on the same IP.