In her thirty-five-year long career, Lončar was a member of management teams of prominent Slovenian and international companies in several sectors: mobile communications, retail, industry, and utility. Lončar acquired experience in the area of strategic development, sales and marketing.
During her eighteen-year career at Siemens, successfully managing Siemens in Slovenia for fourteen (14) years and Siemens in Croatia for three (3) years, she has been actively involved in many strategic projects in the countries as well as in the Adriatic region. Since October 2021, Medeja Lončar is also leading Siemens Serbia in addition to her current roles. Lončar has given special emphasized in her work for to the concept of Industry 4.0. and bringing the Siemens customers in the new era of digitalization. 
Owning to her engagement and executive position in various chambers and associations, including her President roles in Management board at Slovenian Managers’ Association and in Supervisory board of German-Slovene Chamber of Industry and Commerce as well as being a Management Board Member German-Croatian Chamber, she actively contributes to progress in society by advocating on topics of sustainability, digitalization and industry 4.0, female representation in managing roles as well as in engineering, business ethics and change management.