<p>Boredom is on the rise, indicating an urgent need to understand its nature and impact. While there is broad agreement on the negative affect associated with its experience, its typical level of arousal remains heavily contested. Therefore, we conducted a three-level random-effects meta-analysis on the boredom-arousal relation across multiple domains. This study was pre-registered via <a href="https://osf.io/db3wz">OSF</a> on April 4th, 2024, and we provide the data, the coding manual, and the analysis code at <a href="https://osf.io/45zuh/">https://osf.io/45zuh/</a>. The databases Web of Science, PsycInfo, PubMed, and ProQuest Dissertations &amp; Theses Global were searched on the 27th of November, 2023. We included all quantitative correlational and experimental studies that targeted human, non-clinical participants and provided effect sizes on the boredom-arousal relation or information to calculate effect sizes. Overall, 214 effect sizes from 72 unique samples that comprised a total of 6570 participants fulfilled the inclusion criteria. Correlational evidence (<i>i</i> = 75 effect sizes) suggested that more intensely experienced boredom was related to reduced arousal, <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\bar{r}\)</EquationSource> <EquationSource Format="MATHML"><math> <mover accent="true"> <mrow> <mi>r</mi> </mrow> <mo>¯</mo> </mover> </math></EquationSource> </InlineEquation> = −.13, 95% CI [−.22, −.05]. Experimental evidence (<i>i</i> = 122 effect sizes) showed that boredom was associated with significantly lower arousal as compared to various control conditions; <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(\bar{d}\)</EquationSource> <EquationSource Format="MATHML"><math> <mover accent="true"> <mrow> <mi>d</mi> </mrow> <mo>¯</mo> </mover> </math></EquationSource> </InlineEquation> = −0.40, 95% CI [−0.59, −0.22]. However, there was significant heterogeneity in effect sizes, and the relation between boredom and arousal was moderated by the type of boredom measure, the type of arousal measure, and the type of control group in experimental designs. Specifically, the relation was not significant when boredom measures included items that denoted mixed or high arousal, when arousal was assessed via heart rate variability, or when experimentally induced boredom was contrasted with a neutral control condition (e.g., waiting, doing nothing). The assessment of study quality, testing publication status as a moderator, as well as visually and quantitatively assessing funnel plot asymmetry indicated minor to no risk of bias. Implications for the theoretical conceptualization of boredom and future research are discussed. The authors received no external funding for this work.</p>