Acid-sensing ion channels (ASICs) are proton-gated cation channels that are expressed in many tissues. ASIC1a is one of the most pH-sensitive subtypes and is involved in ischemia-induced cell damage and pain. The first described potent inhibitor of ASIC1a, PcTx1, is a single inhibitor cystine knot peptide from tarantula venom. Subsequently, Hi1a, a 75-residue double-knot peptide identified from a venom-gland transcriptome of the Australian funnel-web spider Hadronyche infensa, was found to be a more selective ASIC1a inhibitor. Inhibitors of ASIC1a are remarkably neuroprotective and cardioprotective in rodent models of ischemic stroke and myocardial infarction, respectively, making them promising drug leads. We reveal that double-knot ASIC1a inhibiting peptides are a common feature of Australian funnel-web spider venoms and show high avidity inhibition of ASIC1a by three funnel-web spider venoms. This represents the largest known family of venom derived double-knot peptides with ion channel activity. Our work shows that Australian funnel-web spiders have recruited and diversified bivalent double-knot ASIC1a inhibitors over single-knot peptides in their venoms and that they are present in amounts sufficient to contribute to the effects of injected venom. This strongly suggests that the targeting of ASICs by venom peptides is likely to be of ecological importance, rather than an accidental off target activity. Understanding the ecological role of this family of peptides will shed light on the physiological roles of acid-sensing ion channel 1 and aid in the development of these peptides as valuable research tools and viable drug leads.