The import of nuclear-encoded proteins into mitochondria is a key process for the right mitochondrial function. The evolutionarily conserved translation factor eIF5A is primarily known as an elongation factor which binds ribosomes to facilitate the translation of motifs with polyprolines or combinations of proline with glycine and charged amino acids. eIF5A expression is up-regulated by the transcription factor Hap1 under respiratory conditions and is essential to maintain the mitochondrial activity. Here we identify an essential polyproline-containing protein as a direct eIF5A target for translation: the mitochondrial inner membrane protein Tim50, which is the receptor subunit of the TIM23 translocase complex. We show how eIF5A directly controls the mitochondrial protein import through the alleviation of ribosome stalling along Tim50 sequence at the mitochondrial surface. Thus, the absence of eIF5A leads to the accumulation of mitochondrial protein precursors in the cytosol as well as to the induction of the mitoCPR stress response. Moreover, we show that eIF5A also affects mitochondrial functionality by reducing the translation and levels of many mitochondrial proteins. Overall, these results show for the first time how ribosome stalling negatively impacts the mitochondrial import process and explain why eIF5A is essential for the mitochondrial function.