Klebsiella (K.) pneumoniae is a major pathogen in human and veterinary medicine, known for its high resistance rates. Comprehensive resistance data are essential to combat global antibiotic resistance. This study aims to (a) document the prevalence of resistant K. pneumoniae and (b) assess the utility of routine laboratory data for passive monitoring. We analyzed a dataset of 175,171 samples from diseased dogs and cats in Germany collected between 2019 and 2021, identifying 1185 K. pneumoniae isolates with measurable minimum inhibitory concentration values. We evaluated resistance rates to a third-generation cephalosporin (cefovecin) (16.3%), chloramphenicol (16.1%), doxycycline (13.9%), enrofloxacin (8.9%), gentamicin (6.0%), nitrofurantoin (24.8%), and sulfamethoxazole-trimethoprim (15.0%). Notably, feline K. pneumoniae isolates from the urinary tract showed a high cefovecin resistance rate of 70.0%. Comparing our findings with third-generation cephalosporin-resistant human isolates from the Antimicrobial Resistance Surveillance database (ARS) maintained by the Robert Koch Institute revealed a lower resistance rate (7.7%). This study presents Germany’s most comprehensive dataset on K. pneumoniae resistance in companion animals over a three-year period. These findings can strengthen national resistance monitoring efforts and enhance data interpretation through substantial datasets.