Can I Use 3rd Party Theme In Blogger?

The answer is "Yes". You can use any theme as you want even it's 3rd party. Blogger doesn't stop you to use. However, there are some pitfalls you should know before you use 3rd party theme. One of them is the Blogger help community forum doesn't support 3rd party themes unless it's a Blogger-provided theme like Contempo, Soho. It doesn't mean you can't use 3rd party theme. Picking a good or SEO-friendly theme is always better. Because it does affect SEO. And you should care about it.