The actress stopped in the small town of Esslingen, near Stuttgart, while in Germany promoting her latest movie One For The Money.
Heigl explored her ancestry with her mum Nancy, who was delighted to tour the house where her father Reinhold F. Engelhardt lived before emigrating to the U.S. in the 1920s.
Heigl was greeted by her cousins at a civic reception in Esslingen's Old City Hall, where Mayor Juergen Zieger presented her with gifts including documents tracing her family roots.
She told reporters, "I worked in Germany when I was 17 in Berlin. This will be my second time in Germany, so it still feels like another country to me, but being here in Esslingen feels very emotional because of the history we have here."
Heigl later signed autographs and posed for pictures with fans as well as a newlywed bride who had just married in the City Hall.
The Knocked Up star's mother Nancy insisted her daughter was always home by 1am in a bid to keep the blonde beauty out of trouble, and the actress always adhered to the rule - because she feared she'd be enrolled in a Swiss nunnery if she didn't make it home on time.
In a family interview with Elle magazine, Nancy explains, "Katie believed it for a very, very long time, and that's the most important thing. I believed I would do it, and she believed I would do it... We go to Switzerland. We go to the bottom of the mountain. We take away all her clothes, we put her in a cloth sack, we put her on a donkey and send her up to the top of the mountain, where she doesn't get to talk to anybody on a regular basis but will occasionally get a letter from me saying, 'How you doing?'"
But the star confesses she finally got fed up with her mum's rules and moved out at 22 after realising all her pals weren't tied down by the same restraints.
The actresses adds, "I had this boyfriend, and we were really serious. I'd be over at this house and it would come around one, and I'd be like, 'I gotta go. I got this curfew.' One night, he just looked at me and was like, 'What the hell is wrong with you?'"
The Knocked Up star and her mum Nancy have each put up $850,000 (£531,250) to buy a total of eight top condominiums in Sherman Oaks, California.
Each unit features hardwood flooring, granite kitchen counters, balconies and fireplaces, reports TMZ.com.
Katherine Heigl has made plans to stop puffing on her electronic cigarette long enough to produce and star in her very own HBO movie, called The Knitting Circle. In Craig Wright's adaptation of the best-selling Ann Wood book, Heigl will play the main character -- a woman who is married and eases her grief over the death of her daughter by participating in a knitting circle. Heigl's mother, Nancy, will produce as well, which makes sense considering she also produced two of her daughter's other movies, Life as We Know It and The Ugly Truth. So here's to mother-daughter projects: because if they don't tell the hard stories (like the ones where women find hobbies to cope with an extreme loss, or the ones where a woman finds herself having to talk through her orgasms when she's out to dinner with her friends and family because a particularly vindictive man is controlling the vibration speed of her pearl thong (and he knows just how she likes it)), then who will?
The Knocked Up star and her singer husband Josh Kelley welcomed baby Nancy Leigh into their family from Korea last September (09), when the baby was 10 months old.
Heigl revealed the tot, nicknamed Naleigh, had special needs, as well as a congenital heart defect. The baby underwent life-saving surgery when she was just two months old to repair a hole in her heart.
The baby girl had another operation just before Heigl took her home to Los Angeles and the actress insists Naleigh is now in perfect health.
She tells Harper's Bazaar magazine, "Her heart is 100 per cent fine now. She has a scar, so she won't be wearing bikinis, which is fine by us."
And Heigl is adamant being a mum to a special needs baby isn't as tough as it may seem.
She adds, "A lot of children don’t find forever homes because they’re on that special-needs list, even if it’s because of something as simple as her mother smoked cigarettes for a month, not knowing she was pregnant. That’s not so huge (a problem) that you couldn’t handle it."
Heigl and her singer husband Josh Kelley finalised the adoption of 10-month-old Nancy Leigh from Korea last month (Sep09).
The happy news came days before Grey's star Ellen Pompeo became a first-time mum and welcomed a baby girl with husband Chris Ivery.
Knight, who is openly gay, now admits his former castmates have him brooding for a child of his own.
Asked about Heigl's new daughter, he tells U.S. TV comedienne Ellen DeGeneres, "I want a baby. I don't know if it's going to end up working out, but that would be something I would like... I've wanted (kids) for a while, so (she) reinforces it."
Two and a Half Men star Jon Cryer and his wife Lisa Joyner have adopted a baby daughter.
Just a week after Cryer cryptically mentioned his "baby girl" during his Best Supporting Actor acceptance speech at the Emmy Awards, the 44-year-old's publicist has confirmed that he's a dad again.
Baby Daisy, born on Aug. 11, is Cryer's first child with 42-year-old Joyner, who he married in 2007.
The actor has a 9-year-old son, Charlie, from his first marriage to Sarah Trigger.
Cryer is the second TV star in as many weeks to adopt -- Grey's Anatomy star Katherine Heigl and her husband Josh Kelley took custody of 10-month-old Korean girl Nancy Leigh earlier this month.
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Just a week after Cryer cryptically mentioned his "baby girl" during his Best Supporting Actor acceptance speech at the Emmy Awards, the 44 year old's publicist has confirmed he's a dad again.
Baby Daisy, born on 11 August (09), is Cryer's first child with 42-year-old Joyner, who he married in 2007.
The actor has a nine-year-old son, Charlie, from his first marriage to Sarah Trigger.
Cryer is the second TV star in as many weeks to adopt - Grey's Anatomy star Katherine Heigl and her husband Josh Kelley took custody of 10-month-old Korean girl Nancy Leigh earlier this month (Sep09).
The Knocked Up star and her singer husband Josh Kelley finalised the adoption of 10-month-old Nancy Leigh from Korea last week (ends18Sep09), revealing their applications were fast-tracked because the tot has special needs.
Heigl explained, "They wanted to get her to us as quickly as possible."
Now the National Enquirer reports the baby - nicknamed Naleigh - had an operation soon after she was born to fix her heart defect.
A source tells the tabloid, "Doctors said the congenital heart defect had to be treated quickly to save the baby's life."
The couple have named their first child Nancy Leigh, after the actress' mother Nancy and her sister Margaret Leigh, but have already nicknamed her Naleigh.
Heigl and Kelley began the adoption process for little Naleigh - who was delivered on 23 November (08) - six months ago.
The Grey's Anatomy actress revealed earlier this month (Sep09) the couple's applications were quickly processed, because their daughter has special needs.
Heigl explained, "She is a special needs baby and because of that it all moved so much faster. They wanted to get her to us as quickly as possible."
A spokesperson for the actress says both parents and child are together and doing well.
The couple has been married since 2007.