Pokémon: where to begin watching?

I’d start with the original series. If he likes that, show him the movie. Just be prepared, that movie packs a surprising amount of emotional weight. It was similar to the 80’s animated Transformers movie for kids that grew up in the 90’s.

Personally, though, prepare to hate the show. I enjoyed it in a “so bad it’s good” way when I was 12, and I thought ROTS was better than A New Hope.

The first season is on Netflix (Indigo League). Between Amazon Prime and Netflix there are a lot of other seasons free, and some free movies.

Start on the first season for sure. After that, it's not the end of the world if you don't go in order because not all of them are free. At the end of each big region arc, Ash leaves his Pokemon behind except for Pikachu and goes to a new region to start over, so it's not like you're going to be confused if you watch Indigo League and then jump to the Hoenn region.

S1 - Indigo League
S2 - Orange Islands
S3-S5 - Johto League (Gold & Silver)
S6-S9 - Hoenn Region (Ruby & Sapphire)
S10-S13 - Sinnoh Region (Diamond & Pearl)
S14-S16 - Unova Region (Black & White)
S17-S19 - Kanto Region (X & Y)
S20-S22 - Alola Region (Sun & Moon)
S23 - Pokemon Journeys (Go/Galar)

Netflix has some of these free. Amazon Prime has others. You used to also be able to go to Pokemon.com and they had some episodes always available while they cycled through weeks at a time of older seasons. The movies tend to be made to be stand alone but Pokemon The First Movie (Mewtwo) is the very first original one and meant to be seen at the end of Indigo, and Pokemon I Choose You is the first of the newly rebooted movies and it retells/reimagines Ash and Pikachu's story a bit.

Thank you to everyone for the advice. I added Indigo League to our list on Netflix; we'll see if it sticks.

tGOAT theme song:

LINK