Born in Angeles City, Philippines, Santos played for Lubao Institute during his high school career and won the West Central Zone Championship.

He was also named Defensive Player of the Year and was part of the Mythical Five together with season MVP Yap, Rich Alvarez, Paul Artadi, and Reynaldo Mendoza.

He would win the Most Valuable Player award the next season (2004) but the Tamaraws lost to the De La Salle Green Archers in three crucial games.

In his last year (2005) in the UAAP, he again led the team to the title by sweeping the Green Archers in an anticipated championship rematch against La Salle, thereby giving the Tamaraws a three-peat from 2003 to 2005.

He was adjudged PBL MVP of the tournament and was part of the 2004 Mythical Five alongside former PBA players Jojo Tangkay and Chester Tolomia and teammates Miranda and Isip.

In 2006, he led Magnolia Ice Cream to the PBL Heroes Cup title, coming back from 0–2 deficit to defeat Welcoat Paints.

[2] During the off season Arwind Santos finally got his wish to play for the San Miguel Beermen, the winningest team in the history of the Philippine Basketball Association.

None among the officials confirmed the trade although a highly placed source revealed that Santos was shipped to the Beermen in exchange for 6'5" power forward Marc Pingris, 6'6" sophomore center Ken Bono and San Miguel's 2010 first round pick.

[7] In the 2012–13 season, Santos led the Petron Blaze Boosters to a runner-up finish in the season-ending Governors Cup against the San Mig Coffee Mixers in a series that went the distance, 3–4.

While his team lost the championship, Santos won his second BPC award in the season-ending Governor's Cup by edging out teammates June Mar Fajardo and Alex Cabagnot.

He won his first-ever MVP award with a total of 2,840 points beating out Barangay Ginebra's LA Tenorio (2,819) and Talk N' Text's Jayson Castro (1,682).

In the Philippine Cup of the 2014–15 PBA season, Santos led the San Miguel Beermen to the championship alongside current MVP June Mar Fajardo in a grueling 7-game series against the Alaska Aces.

"[12] PBA commissioner Willie Marcial sanctioned Santos with a ₱200,000 fine, 100 hours of community service and to undergo counseling on equality and racial discrimination.

[20] As of the end of 2022–23 season[21][22] He also suited up for the Philippine National Team a couple of times under coach Chot Reyes in 2006 with the likes of LA Tenorio and Joseph Yeo and competed in the 28th Jones Cup but didn't make it to the final line up in 2007.

In August 2010, Santos, along with other PBA players, was considered as a possible reinforcement for Smart Gilas, as the developmental Philippine national basketball team was looking to make the squad more competitive.

Making up the PBA All-Stars line-up were PBA legends Alvin Patrimonio, Allan Caidic, Ronnie Magsanoc, Benjie Paras and Kenneth Duremdes and active players Santos, Wynne Arboleda, Japeth Aguilar, Dondon Hontiveros, Jay-R Reyes, Marc Pingris, Enrico Villanueva, Sonny Thoss, Willie Miller and Joseph Yeo.