Background <p><i>Borrelia</i> (<i>B</i>.) <i>valaisiana</i> is a tick-borne spirochete within the <i>Borrelia burgdorferi</i> sensu lato complex. In Sweden, it occurs in <i>Ixodes ricinus</i> ticks, but its role as a human pathogen remains uncertain. In the Tick-Borne Diseases STING study conducted during 2007–2015, adult participants from Sweden and the Åland Islands, Finland, provided ticks, blood samples for serological analyses, and questionnaires at inclusion and at a 3-month follow-up. Medical records were reviewed for those seeking care. Ticks were characterised, feeding duration assessed, and pathogens detected by real-time PCR. During 2008–2009, <i>B. valaisiana</i> was identified by PCR in 1.6% (34/2,154) of the ticks. Since its significance as a human pathogen is unclear, we chose to examine this tick-bitten cohort in greater detail. Accordingly, the objective of the study was to assess whether participants bitten by <i>B. valaisiana</i>-positive ticks developed Borrelia-specific antibodies and/or symptoms suggestive of infection.</p> Materials and methods <p>Participants bitten by <i>B. valaisiana</i>-positive ticks (VPOS, <i>n</i> = 33; one bitten twice) were compared with an age- and sex-matched group bitten by Borrelia-negative ticks (VNEG, <i>n</i> = 67). Borrelia-specific IgG was analysed in paired blood samples.</p> Results <p>Median age in VPOS was 67 years; 58% were women. Seroconversion for Borrelia-specific IgG occurred significantly more often in VPOS than VNEG (<i>p</i> = 0.03). Common symptoms in VPOS included neck pain, myalgia/arthralgia, numbness, and headache, but none sought medical care. No significant difference in symptom occurrence was observed between groups.</p> Conclusion <p>Tick bites involving <i>B. valaisiana</i> were associated with higher Borrelia antibody seroconversion, without significant symptom associations or need for medical intervention. The results of this study provide new insights into the potential human impact of <i>B. valaisiana</i>.</p>