SUMMARY: The success of plant reproduction depends on the timely transition from the vegetative phase to reproductive growth, a process often referred to as flowering. Although several plant‐specific transcription factors belonging to the Teosinte Branched 1/Cycloidea/Proliferating Cell Factor (TCP) family are reportedly involved in the regulation of flowering in Arabidopsis, the molecular mechanisms, especially for Class I TCP members, are poorly understood. Here, we genetically identified Class I TCP7 as a positive regulator of flowering time. Protein interaction analysis indicated that TCP7 interacted with several Nuclear Factor‐Ys (NF‐Ys), known as the 'pioneer' transcription factors; CONSTANS (CO), a main photoperiod regulator of flowering. SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) was differentially expressed in the dominant‐negative mutant of TCP7 (lcu) and the loss‐of‐function mutant of Class I TCP members (septuple). Additionally, we obtained genetic and molecular evidence showing that TCP7 directly activates the flowering integrator gene, SOC1. Moreover, TCP7 synergistically activated SOC1 expression upon interacting with CO and NF‐Ys in vivo. Collectively, our results provide compelling evidence that TCP7 synergistically interacts with NF‐Ys to activate the transcriptional expression of the flowering integrator gene SOC1. Significance Statement: We demonstrated that TCP7 promoted flowering by interacting with NF‐Ys and CO and directly binding and regulating the expression of SOC1 in plants, which broaden our understanding of the regulatory mechanism of plant flowering transition, the function of NF‐Ys and plant‐specific transcription factor Class I TCP. [ABSTRACT FROM AUTHOR]