Is it possible to serve in multiple branches of the military ?

You can do different nations if you really want to get froggy. I started in the British Army, then USMC, then NC Guard. Serving in different nations isn’t uncommon in the British Commonwealth and i met lots of folk in the Guard that had been in. The other services including coasties. Quite common for Army and Marines to switch also.

Keep in mind not every service is eager to accept prior service members, often it can come with a voluntary reduction, which if you make a career out of this can affect you in income and retirement.

Enjoy it while you got it..there's nowhere to go from "UP".. I actually had 4 schools under my belt, if they REALLY wanted to count em up in 90 when I ETS'd totally..basic [1] AIT for Chapparal [ 2 OSUT at Bilss] a 54E, Divisional NBC school, Camp Casey, Korea, prior to service in the NBC room for D 2 -61 ADA, [3]. and 11 B relcass at McCoy 89..[4]. Didn't help the rank points or pay, but I knew i did it well..that's all that really counts. Wether the Military recognises it with hard stripe or not..

While stationed in Thailand in 1972, a Chief Master Sergent, who was our first sergentwas assigned to our squadron. He had over 30 years in both the ARMY and Air Force. Didn't know what his original AFSC (MOS) was, but he finished 24 years in the ARMY as CSM. He knew a lot about aircraft maintence, so he was most likely in aircraft maintence.

It is possible to serve in two branches of the Armed forces. I did it 6 years active duty in the Navy in a Weapons rating, and after being out for a little over a year I went into the Army as a Bandsmen. I would say concentrate on your first enlistment, and see how it goes, you may like it in the Branch of service you've selected. There are some disadvantages to changing services, most likely it will include a reduction in Rank, and you may or may not have to go through Basic training again depending on which Branch you are going from, and which you are going to. Going from Navy to Army I didn't have to do Basic training again, but it might be different the other way around.

About half of my company at USCG boot camp were prior service; from all branches. After that, there was always at least one prior service guy at each unit I was assigned to. Even one unit that was only 24 people strong had one prior Navy guy.

Serve out your first term. If you still want to, go see a navy recruiter and fill out a dd form 368 and submit through your chain of command. Try to get that 368 around mid august as new job slots open generally on 1 october.

Is it possible ? Sure. I have met people who have been two or three branches. met a USAF COL that was enlisted in he Army and Marines, also fought in Korea....maybe no longer relevant. A buddy from college went AD enlisted Navy, ETSed, went to college, joined the ARNG, then transferred to the ANG, retired as a MSGT. Probable? Unlikely. Considerations
- the USMC doesn't recognize anyone else's basic training. You will do it again for them. Recommend you start there if this is your goal.
- you will likely lose rank each time you hop.
- your MOS in one is a consideration for another.
- it will likely take you four enlistments to do this. Renetry is tricky. That is 12-16 years. Do you want to be a 40+ year old PFC? Also consider that you may rack up injuries along the way.
- if commissioning is in there anywhere, that is something that varies widely over time based on needs of the service. It will likely be the terminus of this junket. Officers branch transferring is difficult. I have seen two succeed (Army Infantryman to Navy Helo Pilot the other was an Army Warrant Attack Pilot to USCG Helo pilot).
- reclassifying inside a service happens, but it is always to an understrength MOS, vice "hey! That's cool I wanna do that!". Used to be the BEAR program in the Army. If your MOS is thin, you won't be able to leave. If the gaining MOS is overstrength, you won't be able to leave.

Would recommend you focus on the one at hand and see what happens. Positive performance opens doors.
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Yes, I joined the Navy at 17, in boot camp we had a soldier and a marine going thru with us. After I came off active duty I went into the army with my younger brother. Served 3 active Navy and 8.5 yrs active Army.

Absolutely YES - I served 10 + USMC, 8 + Nati0nal Guard, 7 mos Active AF, 3 1/2 Air Force Reserves - total just over 22 years

yes it is possible - I have met many that have served in a different branch before joining the Army - I have met folks that were in the Navy, Marines, and 1 prior Air Force. Not sure how difficult it would be now, as both the Air Force and Navy do not have MOS's that combat arms would fit into.

https://www.stripes.com/news/20-years-4-branches-servicemember-is-part-of-exclusive-club-1.298471

This guy served in four branches! Admittedly in the reserves...

Of course you can serve in more than one branch or component. I started with four years active Air Force, did a year Army National Guard, four years Active Army, then a long break in service while I earned my Bachelor's Degree and worked as an Army and Air Force Contractor. Then another year Army National Guard, and finally the past 12+ years in the Air National Guard. And for the past 14 years I volunteer with the Coast Guard Auxiliary, and recently joined the Civil Air Patrol as a volunteer pilot. So yes, you are never tied to just one branch or component of the military.

Been there done that
Just give your current Service a chance, and later consider MOS switch VERY carefully

Yep. Four years in the USN, the last 15 in the Army.

It's possible, but keep in mind that every time you switch branches you'll be demoted down to an entry-level pay grade. I definitely wouldn't want to spend a career being paid E-4 salary the whole way through. As long as you like your MOS, sticking to it for E-7+ is the way to get proper compensation for your skills.

When I was at FT Hood in 75 had an E-5 that had been in 4 of the 5 branches, then in 80 in Germany had a medic that used to be in the Marines and switched to Army.

Yes, but time in grade required in each service depending on the MOS may slow promotions. But not always. Have a good friend who went through the Marine Corps PLC (Platoon Leader Course) sort of like ROTC, in college. After completing OCS and TBS, went to flight school. Flew A4 Skyhawks in Vietnam. Transitioned to the Marine Corps Reserve, as a captain, and went to medical school. After med school transferred to the Navy (the Marine Corps does not have its own medical personnel) and became a flight surgeon. Some years later, transferred to the Air Force as a flight surgeon. Retired as a Colonel. His promotions came with no delay but of course due to the specialty. Additionally, moving from Lt. Col. to Colonel was very competitive. He said that the reason he made the cut was due to the fact that the general making the decision said it was his duty as a combat fighter pilot and that he had maintained flying status as a flight surgeon.

I've had multiple friends serve in another branch before crossing over to the Air Force...so in short, yes it's possible.

I served in the Navy, Army, and Coast Guard from which I retired. I definitely saved the best for last.