His music was conservative, concentrating mostly on pop song standards, polkas, and novelty songs, delivered in a smooth, calming, good-humored easy listening style. His show was warm and family-oriented. His Champagne Music has been considered the epitome of "square".

In the 1920s, Welk led big band engagements in the eastern South Dakota area. His band was the station band for popular radio station WNAX in Yankton, South Dakota. During the 1930s, Welk led a travelling big band, specializing in dance tunes and 'sweet' music. The band performed in many places across the country, particularly in the Chicago, Illinois area. In the early 1940s the band travelled to California for a six-week engagement at the Aragon Ballroom at Venice Beach. This gig turned into a 10 year stint, drawing crowds of nearly 7000 on a regular basis.

In 1952, Welk settled in Los Angeles, California. That same year, he began producing The Lawrence Welk Show on KTLA in Los Angeles. The show was first aired nationally on ABC in 1955. Welk's television program had a policy to only play well known songs and tunes from previous years, so that the target audience would only hear numbers that they were already familiar with. This strategy proved commercially successful.

Much of the show's appeal was Welk himself. Although born in the United States, he spoke with a slight but notable European accent that many, especially ladies, found to be quite appealing. While his English was quite passable, he never did grasp the English idiom completely, and was thus famous for his "Welk-isms", such as "George, I want to see you when you have a minute, right now". His TV show was recorded as if it were live and was sometimes quite free-wheeling. Welk often took ladies from the audience for a turn around the dance floor. During one show Welk brought a cameraman out to dance with one of the ladies and took over the camera himself.

The reputation for "corny music" notwithstanding, his musicians were always top quality, including accordionist Myron Floren and New Orleans Dixieland clarinetist Pete Fountain. Though Welk was occasionally rumored to be very tight with a dollar (and indeed, could be on occasion,) he payed his regular band members top scale - a very good living for a working musician. Welk was noted for spotlighting individual members of his band and show. His band was well-disciplined and had excellent arrangements in all styles. One notable showcase was his album with the noted jazz saxophonist Johnny Hodges. Welk had a number of instrumental hits, including a cover of the song "Yellow Bird". His highest charting record was his recording of "Calcutta". Welk himself was indifferent to the tune, but his musical director George Cates said that if Welk did not wish to record the song, he, (Cates) would. Welk replied: "Well, if it's good enough for you George, I guess it's good enough for me". Despite the emergence of rock and roll, Calcutta reached number 1 on the U.S. pop charts in 1961, and was recorded in only one take.

Even though it never lost touch with its big band origins, the Lawrence Welk show fully embraced changes on the musical scene over the years. The show continued to feature fresh music alongside the classics for as long as it existed, even music originally not intended for the big band sound. (During the 1960s and 1970s, for instance, the show incorporated material by such contemporary sources as The Beatles, Burt Bacharach and Hal David, The Everly Brothers and Paul Williams, albeit in the Welk's signature Champagne style.) The show, which was originally in black and white, later went to color in the mid-1960s. In time it would feature synthesized music and, towards the end, early green screen technology that would add a new, if now somewhat cheesy, dimension to the story settings sometimes used for the musical numbers.

Welk was married for over sixty years, until his death, to Fern Renner, who bore him three children. One of his sons, Lawrence Welk, Jr., ended up marrying fellow Lawrence Welk Show performer Tanya Falan.

Welk's California automobile license plate read A1ANA2, referencing his trademark count-off before each number, "A one, and a two..." This plate is visible on the front of a Model A Ford in one of the shows from 1980.

His band continues to appear in a dedicated theater in Branson, Missouri even though Welk is now deceased. In addition, the television show has been repackaged for broadcast on PBS stations, with updates from show performers appearing where commercial breaks were during the original shows. The repackaged shows are broadcast at roughly the same Saturday-night time slot as the original ABC shows, and special longer Welk show rebroadcasts are often shown during individual stations' fund-raising periods.

A resort community in Escondido, California, developed by Welk and promoted heavily by him on the show, is still named for Welk.

Welk is said to have learned English only when he was already an adult because he always spoke German at home. When he was asked about his ancestry, he replied always with "Alsace-Lorraine, Germany"; although not strictly correct, many German-Russian and German-Ukrainian Roman Catholics have roots or links to Alsace-Lorraine, and identify themselves as such.

He died from pneumonia in Santa Monica, California at the age of 89, and is buried in Holy Cross Cemetery in Culver City, California.

Lawrence Welk is a recipient of the state of North Dakota's Roughrider Award.