Nathan attended Aitkin High School where he was a four year varsity athlete in football, baseball, and basketball. He is the all time leading scorer in Aitkin Basketball program history. Ehnstrom threw a no hitter his sophomore season and helped lead his team to its first baseball State Tournament where he was awarded All State.

Ehnstrom attended the University of Northwestern Saint Paul where he was a four year starter, excelling both on the mound and defensively. Nathan posted a .1000 fielding percentage his senior season in 150 chances. He also played all 9 positions in his final regular season game of his career. Nathan was awarder All Conference awards as both a pitcher and utility player.

As a coach Nathan has done one year of private instructions, and he has also helped out with camps in Aitkin. He coached a 12u team in Aitkin and has worked as a personal trainer for half a year.  Ehnstrom coached the 13u team this fall 2018 in his first season with the Icemen.