I was given per diem from my company but was taxed on it. Is there any way to claim or get that taxed per diem back?

Assuming the per diem was a reimbursement for work related travel, including meals. you may have a deduction for travel expenses that can be used to offset the income through itemized deductions.  Use Deductions & Credits for all itemized deductions.

In TurboTax for job related expenses specifically do the following:

• In the search box type employee business expenses
• Jump to employee business expenses
• If you are a transportation worker be sure to check that box for special allowances
• follow the prompts DO NOT enter any reimbursements that were included in box 1 of your W2.*

* I have included a screenshot showing you this section.

No. Starting in 2018 W-2 job related expenses are no longer deductible. So if the per diem was included in box 1 of your W-2, it's taxable income to you.

You may wish to talk with your employer about an "accountable" reimbursement plan. This is a plan where you provide the employer receipts for your qualified W-2 job related expenses and they reimburse you. Then the amount reimbursed is not included on your W-2 and you therefore don't get taxed on it.