Yes, it will, when you have a declined mortgage application on your credit file it will affect your score, however this is often just temporary.
When you apply for a mortgage, your lender will do a hard credit score and this will be visible on your credit file. If this application declines and then you apply again, your new lender will see that you’ve just had a recent decline and wonder why.
Firing off multiple mortgage applications and being declined could impact your ability to get accepted for a mortgage due to the number of hard searches on your credit file.
Utilising the services of an experienced mortgage advisor will improve your chances of being accepted for a mortgage utilising their experience and knowledge of lending criteria and products.