|European Indoor Championships|
|2015 Prague||Long jump|
Marincu grew up in Deva, Romania, a city famous for gymnastics. She was interested in sports and as her physique was not suited to gymnastics she focused on athletics instead. Her international debut came at the senior level when she was aged sixteen. At the 2013 European Athletics Indoor Championships she came 17th, failing to go beyond six metres. She came to prominence internationally with a gold medal double in the long jump and triple jump at the 2013 World Youth Championships in Athletics – becoming only the second athlete to achieve that feat, after her compatriot Cristine Spataru. She ended that year with personal bests of 6.54 m (21 ft 5 1⁄4 in) for the long jump and 13.81 m (45 ft 3 1⁄2 in) for the triple jump.
In her 2014 season, she set a series of personal bests, including 6.71 m (22 ft 0 in) for the long jump, 11.85 seconds for the 100 metres and 7.40 seconds for the 60 metres. Marincu won her first senior medal at the age of eighteen at the 2015 European Athletics Indoor Championships – after a jump of 6.57 m (21 ft 6 1⁄2 in) in the qualifying round, she had a personal best and European junior record of 6.79 m (22 ft 3 1⁄4 in) in the final, which brought her the bronze medal behind Ivana Španović and Sosthene Taroum Moguenara.
- 100 metres – 11.85 seconds (2014)
- Long jump – 6.71 m (22 ft 0 in) (2014)
- Triple jump – 13.81 m (45 ft 3 1⁄2 in) (2013)
- 60 metres – 7.40 seconds (2014)
- Long jump – 6.79 m (22 ft 3 1⁄4 in) (2015)
- Triple jump – 13.34 m (43 ft 9 in) (2013)
|2013||European Indoor Championships||Gothenburg, Sweden||17th||Long jump||5.98 m|
|World Youth Championships||Donetsk, Ukraine||1st||Long jump||6.42 m|
|1st||Triple jump||13.75 m|
|2015||European Indoor Championships||Prague, Czech Republic||3rd||Long jump||6.79 m|
|World Championships||Beijing, China||—||Long jump||NM|
- Minshull, Phil (2013-07-14). Double Donetsk champion Marincu dreaming of emulating Romanian great Cusmir-Stanciu. IAAF. Retrieved on 2015-03-07.
- Mulkeen, Jon (2013-07-14). Marincu secures jumps double as Jamaica tops medals table – IAAF World Youth Championships. IAAF. Retrieved on 2015-03-07.
- Florentina Marincu. IAAF. Retrieved on 2015-03-07.
- Badea, Elena (2015-03-07). CE de sală de la Praga: Florentina Marincu, bronz la săritura în lungime. DC News. Retrieved on 2015-03-07.