Put the Underdog promo code TOPACTION to work for MLB Opening Day 2026, including Arizona Diamondbacks vs. Los Angeles Dodgers on Thursday, March 26, 8:30 p.m. ET on NBC or the Sweet 16 tonight. Underdog offers a simple new-user offer just in time for a full day of MLB and college basketball action: Play $5, Get $50 in Fantasy Bonus Entries.
Sign up as a new user (21+), enter promo code TOPACTION, and play $5 to unlock $50 in Fantasy Bonus Entries. You can use these fantasy bonus entries on more MLB or college basketball games this weekend.
What is the Underdog Promo Code Offer
This Underdog deal is built for new users who want a low-commitment way to try fantasy picks without tying up a big bankroll. You play $5, and you get $50 in Fantasy Bonus Entries, with Underdog promo code TOPACTION.
Timing matters because bonus entries come with a clock. The sweet spot is when the schedule’s packed and you’ve got multiple slates to choose from, like MLB Opening Day or the Sweet 16 on Thursday night, so you can spread out your plays instead of forcing one big card. Whether your first entry hits or not, you get extended funds to play for more cash.
How to Use Underdog for MLB Opening Day 2026 Predictions
Here’s how I’d play Diamondbacks vs. Dodgers (Thursday, March 26, 8:30 p.m. ET on NBC) with a simple, trackable example. If I place a $5 entry, I start by signing up and entering the Underdog promo code TOPACTION. Whatever the outcome of my first entry, I still receive $50 in fantasy bonus entries.
Use your fantasy bonus entries on more MLB action or Sweet 16 predictions tonight.
How to Claim the Underdog Promo Code TOPACTION
It only takes a few minutes to get started before MLB Opening Day and the Sweet 16 on Thursday.
- Head to Underdog with this link and start a new account with your email and phone number.
- On the promo code field, enter Underdog promo code TOPACTION before you finish registration. Double-check it’s applied so your offer tracks correctly.
- Verify your identity and confirm you’re 21+ to unlock deposits and pick'em contests.
- Make your $10 first deposit using your preferred payment method and set your contest or pick’em entry size. Keep your deposit amount aligned with the offer rules so you don’t miss any bonus eligibility.
- Place your $5 first entry on any picks or MLB Opening Day predictions you prefer. You get $50 in fantasy bonus entries to use within Underdog.
If you are located in a legal, sports betting state, don't miss out on the best MLB betting promos to stack thousands in bonus value ahead of Diamondbacks vs. Dodgers at 8:30 p.m. ET on NBC. Underdog ranks among the best DFS sites to use in March 2026.
Terms & Conditions
Must be 18+ (19+ in AL, NE; 19+ in CO for some games; 21+ in AZ, MA, and VA) and present in a state where Underdog Fantasy operates. Terms apply. Offer not valid in MD, MI, NJ, NY, OH, and PA. Concerned with your play? Call 1-800-MY-RESET or 1-800-GAMBLER or visit www.ncpgambling.org; AZ: 1-800-NEXT-STEP (1-800-639-8783) or text NEXT-STEP to 53342; NY: Call the 24/7 HOPEline at 1-877-8-HOPENY or Text HOPENY (467369).
