Czech is mostly syllable-timed, while English is mostly stress-timed and partly constructs rhythm through connected speech processes (CSPs), which cause unstressed grammatical words to change into weak forms. Since these are particularly challenging for speakers with syllable-timed mother tongues, this study addresses the production and perception of weak forms in proficient Czech speakers. In the production part, we examined Czech-accented speakers producing material loaded with grammatical words and CSPs. Subsequent listening analysis confirmed that the more accented the speaker, the fewer weak forms and associated CSPs can be found in their production. In the perceptual part, we used two perception tests containing realisations where CSPs had been manipulated to create one more and one less native-like version of a sentence. Czech respondents were asked to assess comprehensibility and accentedness. The results suggest that comprehensibility is easier for them to assess than accentedness, regardless of whether they had received phonetics and phonology instruction prior to the experiment. Our results correspond with and expand upon previous findings, both for Czech speakers (e.g., Skarnitzl & Rumlová, 2019) and for non-native speakers in general (e.g., Barańska & Zając, 2014), showcasing non-native patterns in Czech speakers. Yet, despite their importance and frequency, CSPs have been given little space in research and teaching.