Jung Eun Lee turned pro and joined the KLPGA in 2007, but her breakthrough year came in 2009. That year she won twice, collected 6 top tens and made over 280 million won, finishing fourth on the year end money list. By far her biggest moment came at the year's second Major, the Shinsegae KLPGA Championship. She wound up in a pitched battle with top KLPGA superstar Hee Kyung Seo for the title. Seo had already won the first Major of the year, the Korean Women's Open. But Lee proved her better this day, winning the Major while Seo finished second. Seo would go on to win the other two Majors of the year, so only Lee prevented her from sweeping them all. Lee played on the winning Korean squad at the 2009 Kyoraku Cup. She achieved one win and one tie during the tournament.

Lee had another pretty good year in 2010. She finished 7th on the KLPGA money list, carding 9 top tens. The highlight of her year was a win at the Hyundai event in September.

Lee had a decent year on tour in 2011, but not as strong as her previous seasons. She did win once, capturing the Nefs Masterpiece title in August. She had two other top tens and earned nearly 200 million won, which left her 15th on the money list.

Lee was a little worse in 2012 on the KLPGA. She had six top tens, with three fourths and two fifths her best finishes. She wound up 24th on the money list.

She started the 2013 season playing in two international events, achieving good results: a 13th at the Swinging Skirts in Taiwan (against a world class field) and a 6th in China at the Hyundai China Ladies Open. She ended up with a solid year on tour, finishing 12th on the money list with about 280 million won earned. She had nine top tens, including runner-up finishes at the Woori Financial and Lotte Mart Women's Open.

Lee finished just 31st on the money list in 2014. Her best result of the year was a tie for 2nd at the Hyundai China Ladies Open. She played LPGA Q-School in the Fall and finished tied for 28th, which earned her conditional status on tour for 2015.

Lee only played three LPGA events in 2015, and earned just $15,000. This enabled her to maintain very limited status for 2016. But in general, she focused on the KLPGA, which was a good idea. She had a good season in Korea, notching her first win in several years and finished 15th on the money list with around 282 million won earned.

Lee won the Samdasoo Ladies Masters in a July in a playoff over So Yeon Park. In Gee Chun was not in the field, but Inbee Park was. It was Lee's fifth career KLPGA win and first in four years. Beside that win, she had six other top tens.

Lee played entirely on the KLPGA in 2016. Her best finish was a runner-up at the Honma Golf Seoul Economy Ladies Classic in late October. She also notched two other top tens and banked a shade under 200 million won for the season, good enough to finish 29th on the money list.

In December, she returned to LPGA Q-School, and this time earned a full card by finishing solo fifth. Lee made the most of her new status by easily having her best season to date in 2017. She made over $350,000 to finish 54th on the money list, maintaining her status for 2018. She had four top tens, including her career best finish of tie for third at the Founders Cup. She also shattered her best scoring average with a 70.88.

2018 was another decent season for Lee, pretty much identical to 2017. She made slightly more money, about $366,000, while finishing slightly lower on the money list, 59th. She had two top tens, but her best finish was probably a tie for 11th she managed at the Evian, the year's final Major. It was her best ever Major result.

Lee also played for the LPGA team at the year ending OrangeLife Champions Trophy team event. She teamed with Inbee Park to square a match, and squared her singles match against Ji Young Kim. The LPGA won 13-11.

Lee had a weaker 2019 season than her previous two years. She made only about $180,000 all year, finishing 81st on the money list. Because she missed the top 80, her status fell from category 1 to category 11 for 2020.

In 2020, the whole world was rocked by the Covid-19 pandemic. The LPGA and KLPGA tours canceled and postponed many tournaments. Jeongeun ended up playing ten LPGA events during the year, missing four cuts. Her best finish was a tie for 23rd at the KPMG Championship. She made a little more than $74,000 for the year, which put her at 94th on the official money list. Fortunately for her, the LPGA decided to allow all players to keep their cards until the end of 2021 because of the pandemic.

Lee had a fairly good 2021 season. She finished 69th on the money list and earned over $263,000. This earned her category 1 status for 2022. She managed her best ever finish, too, when she finished tied for 2nd behind Jin Young Ko at the Cambia Portland Classic. It was her only top ten of the year.

Lee, who was now going by the name Jeongeun Lee5 to contrast with her younger rival Jeongeun Lee6, struggled a bit in 2022. It wasn't a terrible year, and she had a few good moments, but her best finish was only a tie for 25 at the KPMG, and as a result she finished 95th on the money list. She dropped to category 16 for the 2023 season.

Lee had an OK season in 2023. She made around $164,000 and finished 108th on the money list. She had four top 20s with her best finish a tie for 11th at the CPKC Women's Open (aka the Canadian Women's Open). She managed to rise slightly to category 15 for the 2024 season.