Donning traditional attire including lederhosen, Patrick — a model and budding actor who recently starred in "Midnight Sun" with Bella Thorne — enjoyed a big mug of beer as he celebrated turning 25 at Oktoberfest in Munich, Germany, with his dad, 71, by his side.
The men were photographed enjoying themselves at the annual event that Arnold has frequented in recent years (he's from neighboring Austria) and on Sept. 22, the older star — whom TMZ reports has been working in nearby Budapest shooting the upcoming untitled "Terminator 6" sequel — posted a pic of himself with Patrick to commemorate their trip.
"It was absolutely fantastic to celebrate your birthday at Oktoberfest, @patrickschwarzenegger. Great work conducting the band," Arnold wrote.
Also there? Arnold's girlfriend of the last few years, orthopedic therapist Heather Milligan, who also donned traditional Bavarian attire for the celebrations, which will last until early October.
On Patrick's actual birthday, Sept. 18, Arnold honored him with a sweet message and a vintage photo of them together when Patrick was just a little boy. "Happy birthday @patrickschwarzenegger. I love you and I'm so proud of you. I love watching you grow into a great leading man, a fantastic business mind, and an even better human being," Arnold wrote.
Earlier in the week, Patrick posted a goofy photo of himself wearing a blue "It's my birthday" crown as he held up his birthday cake. "Thanks for the birthday wishes 🎂 !! BIG 25! Can't wait for this year. I really think this will be my best year yet!! Got to thank god for 25 years of Health. That's most important! Birthday wishes: more health! More family time! New experiences! More success! Now.. gonna go eat left over cake 🍰:)," he captioned the snapshot.
Patrick's mom, Maria Shriver, also posted a sweet slideshow of photos of them together over the years. "Happy birthday to this amazing young man @patrickschwarzenegger! So fun, so loving, so caring, so full of love and life. Thank you, God, for him. And Patrick, may you celebrate this day you made the world better when you arrived and every day since you have brought love, light and joy to me and your family. God bless you. Love you to the moon and back!" the famed journalist and Kennedy family scion captioned her post.
Maria and Arnold split more than seven years ago but their divorce has yet to be finalized, it was revealed in July.
After Oktoberfest, Patrick flew to Italy where he and his model girlfriend, Abby Champion, attended Milan Fashion Week events.
Arnold appeared to be in great health and spirits at Oktoberfest, which comes less than six months after he underwent open-heart surgery. Complications arose during a less invasive procedure to replace a pulmonic valve that had been put in in 1997 due to a congenital heart defect, requiring the more serious surgery in late March.
"It's true: I'm back!" Arnold tweeted in early April. "I went to sleep expecting to wake up with a small incision and woke up with a big one – but guess what? I woke up, and that's something to be thankful for. Thank you to the doctors & nurses. And I'm truly filled with gratitude for all of the kind messages."